Mercenary conflicting support gems

I found a bladecaster that has on both his damaging abilities brutality support and added chaos damage. Does this effectively mean he does no damage?

It will still do physical damage, but the added chaos damage will do no damage, unless maybe there is some other mechanic involved, but I think since chaos damage can not be converted, it will be doing no damage from that support. I don't know how the supports are picked, but it is likely they are picked from a pool and is possible to get these combinations that may not be desirable.

It can be in some cases that there may be a use for it. For example a lot of Mercs are being used for buffs and having trouble with reflect damage. So doing no damage might sometimes be desirable. In this case chaos does not reflect, so won't be a benefit, but might be doing less phys damage than the Merc would normally do with other supports and be less vulnerable to Phys reflect.

I think it is just a whacky combination though. There's probably other ones as well like void manipulation.

What were his main abilities? They are probably physical (bladefall, blade vortex etc).

Seismic Crush
Bladefall
Blade Vortex
Ethereal Knives
Bladefall of Trarthus

(Pool listed on PoeDB)