Here is a list of defensive and offensive things that you could change on your build. Sorry for how long it is, but there are definite improvements you could make...
1) Your wand is actually terrible... you need huge flat fire and flat fire to spells... as much as you can get... the way spellslinger works, it scales damage with that flat damage way more than spell damage or % fire damage, and the crit roll is pretty much useless to this NON-CRIT build. Your ele overload will be up all the time without that crit on your wand because of the sheer volume of hits you get from VD. my wand has 105-207 flat fire damage, and 17-27 flat fire damage to spells. my fire dam to spells roll isn't great at all, but together those two rolls give a lot of dps.
2) Inpulsa's chest... this is actually a terrible chest for the build, and in the bulid guide it's actually stated a couple times that he was only using the inpulsa's because it dropped for him and he hadn't changed to anything else at the time he uploaded his current gear. it gives you extra clear speed which is nice, but the build is already great at clear speed... Inpulsa's gives you zero bonus vs single target bosses. Try a 6 link Incandescent Heart with 20% ele damage as extra chaos. with that, plus an atziri's flask you can have 35% fire damage as extra chaos... a lot of extra dps and a lot of extra leech from the chaos leech on the flask.
3) You are not using Enduring Cry... this is actually a big mistake... the extra phys damage reduction from the endurance charges is very nice, AND the massive amounts of life regen you get every time it procs can save your save your ass. Spec into Call to Arms for instant warcry, bind it to your left mouse move button, and it will be fully automated. I just hit lvl 91 with my char and have only had 3 deaths. one while leveling, one to bullshit ghost that spawned in a rippy t15 palace map and posessed the boss, and one because i ran a phys reflect map and took out my wave of conviction but forgot to turn off my DD slinger setup, so i killed myself.
4) Invest in a lvl 21 Volatile dead with quality, and a lvl 21 Detonate dead (no quality needed on that one)
5) Get at least 1 regular jewel with "6% chance to knock enemies back on hit" i'm running two of them for double the chance. it's a VERY effective extra defensive mechanic... your barrage and your VD balls will be knocking many monsters back so they can't get to you, and many bosses are not immune to knockback... i've killed many map bosses by just pinning them against a wall with my knockback till they died.
6) flasks: your diamond flask is useless.. this is not a crit build, and even if you had sources of crit multi your crits would still do zero extra damage because of Ele Overload keystone. you do so many hits with your VD balls that Ele Overload is always up anyway, with no extra crit sources needed. I'd replace that diamond flask with a Rumi's flask for extra phys reduction and extra attack and spell block OR with a chemists basalt flask of warding with at least 23% reduced charges used so you get two uses with it. it's quite likely a lot of your deaths can be attributed to curses on your maps. if you get both those flasks you can swap in Rumi's on maps with no curse mods, and the basalt flask of warding on maps with curses.
7) gem links: Personally I never even used the shield charge.. its clunky and i've never felt like i needed fortify with all the other defensive layers i have. Change that 4 link to Flame Dash-Second Wind-Arcane Surge-Enduring Cry, and keep the arcane surge low enough that it will proc every time you flame dash... more dps and more mana regen, plus the enormous defensive benefits of enduring cry.
You are not utilizing the 4th link in your gloves with the 3-link DD slinger setup. You could be running a self cast guard skill like Steelskin for when you're getting hammered or, what i'm doing is running Blood Rage in the 4th socket. I don't use it all the time... the extra attack speed from it is overkill, but you'll get 4% MORE damage from each frenzy charge when you use it... be aware it will delete any energy shield you have, which is why i don't proc the blood rage always. You can also put self cast tempest shield in there if you don't have max block but check the next paragraph before you go that route ***IF you do put a guard skill or blood rage or tempest shield in that extra socket, make sure it is NOT linked with your DD slinger 3-link, or it will increase the mana cost and wipe out your useable mana pool.
8) You haven't taken the 'Sanctuary' group on your passive tree which is a very important attack/spell block cluster... it's right next to Glancing Blows keystone... see #9 below.
9) If a lot of your deaths are one shots there is an easy way to even out the damage you're taking so that one shots will be rare... Spec into Glancing Blows keystone... it's only 1 point on your skill tree to get it. You will absolutely have max block with that, and although you will still take half the damage from attacks/spells that you block, it will make it far less likely for you to get one shot. you should also be able to spec out of Mystic Bulwark and still have max attack/spell block, which gives you the two points you need for the instant warcry node.
10) None of your gems have quality on them. If you have the currency, invest in a bunch of gcps and put quality on your most important dps gems. look up the gems before doing that as some gems will give you no real bonus if you add quality to them.
11) you're not running the suggested cluster jewel setup. You have a large cluster jewel in your pob but it appears that you have none of the nodes on it allocated... though this may be a pob glitch. Also, you should get a large cluster with Sadist and Disorienting Display notables. The blind nearby monsters on Disorienting display is yet another defensive layer.
12) I don't see any source of fire damage leeched as life in your build... your amulet is very nice with the +1 fire skill gems, but try and replace a ring with one that has fire damage leeched as life on it. Right now your only source of life leech is from the chaos damage on atzii's flask, which is not always up.
12) zero life on your shield. really bad life roll on gloves. no life roll on ammy. bad life roll on the diamond ring. (and again, the %crit chance and the cast speed mods on diamond ring are useless to this build. I'd try and replace the diamond ring with a ring that had life, whatever resists you need, plus fire damage leeched as life mod). no life roll on armageddon breath jewel and cast speed roll on it is useless. no life on vivid stone jewel. no life on behemoth solace jewel. you could change belt out for a stygian vice, and get an abyssal jewel in the belt slot with flat life, fire damage to spells, and fire damage to spells while holding a shield on it. (if you had life rolls on every gear item and jewel, then you could spec out of some of the extra life nodes on your tree and still come out ahead)
13) One final suggestion for yet another defensive layer... instead of running two of the recommended small cluster jewels with Surging Vitality, just run one of those and for the other run Disciple of Kitava unique small cluster jewel. It will give you an instant 5% life and mana recovery every 1 second... it can save your bacon, and they're quite cheap. i got a corrupted one with 1% ele penetration for like 15c... even better is one with 'corrupted blood cant be inflicted on you' but those are quite pricey.
Again, sorry for the length of this, but there are a lot of ways you can min-max your dps and defenses. Best of luck!
