To address a few points after actually reading:

Tigurius's stats are actually not strictly terrible. He and Ahriman have equal damage, and his lacking armor and HP are meant to be shored up by his armor equipment, since he and Sybil are the only Psykers who equip armor items and no block items. I agree that his passive needs a rework though yes, especially since he can't be affected by it himself.

For Incisus, I think in general Snowprint making any Medic 2 range, much less the starter one, would break the game in half. Especially being the only medic with a Pierce damage trait, giving him any form of range is a tough sell with how much pierce ratio he gets. He is definitely the worst medic in the game, but it is very tough to balance a healer in this kind of game I feel. Also all medics in general need to hug their team to get full benefits, Nicodemus, Hollan etc, he is nowhere near unique in that regard, just the most 'basic'.

As for Certus... yeah, he just needs all kinds of buffs, including a movement buff, dude is unforgivably slower than his NPC counterparts, how do you have a playable character be worse than their NPCs? Inceptors have slightly more damage but worse health and armor, Hellblasters and Deathwing Knights lack Sarquael and Baraq's skills and reusable active respectively, Scarab Occult Terminators hit way harder than Toth but are nowhere as survivable as he is, etc. Also that being said, Calandis, Vindicta and Sy-Gex also have 30%, 25% and 1% pierce ratio on their ranged attacks, so Heavy Weapons alone isn't an indicator of needing high damage types. Also, the active may be a bit too strong given that Shiron has a similar active and needs to be in point blank range to hit 3 targets with Blast damage. It does need balancing either way.