Regeneration on rares in maps

Was about to wrap up this map; I don't have a terrible character but my economy is bad and I need a ton of upgrades (early mapping). I just bought a tier 5 map because that would be so cool to clear, and instead this tanky mob with regen stopped me from success. The feeling is bad, I've always disliked regen because I usually cannot kill those mobs (feels like I need 3x+ dps and to not be an average player). Report conclusion: felt like a massive gear, knowledge, skill and metagamer check, and 1 rare blocking map completion with absurd tankiness wasn't fun. Not a fan regen at this time. Ps huge fan of the game <3