I've been playing this game since release, so while that doesn't mean much I think it gives me at least SOME credibility. I've seen every stage of these characters and how they perform, and honestly, both Gibraltar and Caustic feel absolutely no different from release.
They both have fortify, a passive ability that reduces incoming damage by 15%. Gibraltar has a delayed 75 hp shield when ads as well.
The problem here though is hitbox. Let's do some math.
Gibraltar has the biggest hitbox size in the game of 79 cubic cm, over twice the size of wraith. This makes him a significantly easier target at all ranges.
Everybody in this game who isnt a die hard mega streamer is going to miss shots when unloading. To put in perspective, if you unloaded ten projectiles against anyone who isnt Caustic or Gibraltar and missed at the very least 1.5 of them, this buff already is completely meaningless to you.
The more bullets you hit that would have missed on a walking marshmallow drastically increases your dps. Even streamers don't always have 85% accuracy or better.
So ironically, a class that has a fortify buff is actually taking more dps than every other character, including ones which has a dps increase buff when taking damage.
But specifically, let's talk Gibraltar.
Gibraltar is, quite literally a juggernaut. He is made for soaking damage, but soaks far too much too quickly to ever be considered viable.
There are a number of reasons why. His hitbox, his gun shield being delayed, his gun shield only covering in front of him, etc. But there are also a number of solutions, which I will propose.
A) We remove the damage fortified buff completely and instead give him armored plates. Gibraltar reduces all damage dealt when hitting these plates by 60%. It would cover his entire back and some of his sides, while only his waist in the front.
This means gibraltar gun shield has more use, it protects his vulnerable front. He can't be ganked as easily either and makes a ton of thematic sense. He already has visual signs of armored plates.
B) Gibraltar loses his fortified buff, and instead gains a flat increase to his health pool of 100. Syringes still restore the same % hp.
Gibraltar gets a tankiness buff, no more % reduction shenangians. Stands more of a chance of the drop. Not a pretty solution but it works
C) Flat out increase his Fortified to 33%
The idea is your dps against an armored target should be reduced. This number needs increased until the dps for missing against an average sized target is lower than when shooting at a gibraltar. I don't like this solution but, it's simple, and it works.
Gibraltar feels like utter shit to play. Every single skill and ability is delayed, he's too big to the point that even with a % damage reduction your dps is increased when shooting at him. Caustic is another problem, but I feel that can be handled far more clearly.