I will preface this by saying that if I'm being honest, Barik is fine in his current state as is. I say this as a Barik main since OB50 or so, with over 1500 games of the character under my belt. No he doesn't have the sustain of Inara/Term/Nando, but he holds his own if you know what you're doing. His damage output is the highest out of every viable point tank in the entire game, his mobility is absurdly good for a point, and he's even more than serviceable as an off-tank (even if OT his ult is actually pretty much useless). Not to mention his skill ceiling is higher than Inara's and probably Nando's (not Term's because his is really high). He just requires you to adjust to his squishiness, and understand that he has the worst sustain out of every viable point in the game.

However there seems to be this (I personally believe very incorrect and sometimes even delusional) mindset that Barik is straight-up worse than every other point option in the game simply because his sustain isn't up to par (which in a sense is true, but that isn't somehow everything). I don't want Barik to be Inara. I don't want him to be Terminus. Which all of these people seem to want. If they DO want buffs for him, I'll suggest the following (trying to make this as minimal as I can):

Increase Max HP from 3400 to 3500.

If sustain is the actual issue, I think a slight buff to his base max hp is in order. Barik's weakness should be his lack of burst sustain, that's by design (which some people don't understand).

Increase the damage of Tinkerin from 480 to 520 and increase its projectile speed by 15%.

I will say: Tinkerin is actually hot trash as a talent that's something I can agree with. It needs more consistent output to not be a downgrade.

Architectonics turret damage boost increased from 20% to 25%.

This will only give him a slight bit more DPS, but every little bit counts and this is his actually good talent at the moment anyways.

Palisade cooldown reduction increased from [.4/.4]s to [.6/.6]s.

I think this buff is absolutely essential to put Fortify on a good level to give these whiners a better sustain option.

Bunker shield health boost increased from [200/200] to [250/250]. Same logic as the Palisade buff.

These are probably what I'd recommend for buffs to him IF I THOUGHT HE NEEDED THEM. Which he really, honestly doesn't. He's fine in his current state even if Tinkerin is actually downright terrible. The problem is that people are too accustomed to him being top 2 in the point tank meta (as he has been for most of the game's lifespan) and they play him like complacent noobs who forget that Barik's main weakness is burst sustain and that you need to actually try to dodge shots instead of face-tanking everything.