Before today, I had 585 hours of gameplay to my name.

At 560 hours, I used Augmented Body 2 for the first time.

Builds work just fine without it, there are other ways to mitigate suppression loss, some of which are you utilising the cover mechanics to fill your suppression bar back up faster, just like the cover systemw as used in 1.0, but even then, suppression on hit, suppression regeneration, focused state, suppression on kill, all of these things existed before the nerf and all of them made playing any build perfectly viable.

You need to take a step back and rethink your approach to the game and your character. It's still perfectly viable, you just have to adapt to it. 

Perhaps if some things are being used mroe than others, make the others better rather than make the good thing not as good.

I can understand you, but ABII was to strong, atleast in my opinion. 

I play an melee crusader and thought at first it would become unplayable, but thats not the case, atleast for me. BUT i had luck with my weapon, and you should look for a weapon with the "HP and Suppression gained on Kill equal to +100% the killing blow's Damage" enchantment.  It can be found on 1h and 2h melee weapons atleast.

This will negate your problems.

Best of luck, hope you will still have fun with the game

nerf or change the way to handle suppression could be reasonable.

but the enchant you metioned is completly shit.

it totally useless in 10+ level mission and boss fight.

it only result you trumble like rat in hunt mission,

while elite take you half hp and suppresion, you have no way to recover

and not way to run.

Look at new stat Suppression Resist Damage Reduce, which is like DR for the suppression bar.  Also there's a passive in the Debuff tree that returns suppression if you knockdown or stun an enemy.

I've done hardest content (on non-seasonal character) with these new changes, it's not as faceroll as before but it's not impossible either.

So, for what should i look forward to keep me alive during high level missions. 

I would like to improve.

it might good on some enchant, especially minor one, not the major 

enchant for any gear

logic is simple: if you are not kill fast,and have enough weak enemy,

 that thing is useless, if you able to kill fast enough, you do not need

it any more.

regen suppresion on focus spend, suppression damage reduction,

suppression regen on hit, energy shield. 

those are much logical than that.

Pair that with the "triple shot" doctrine in a heavy bolter and you have a really fun build, that is maybe a bit squishy but hits hard. They also changed the "triple shot" doctrine by the way.
By removing the suppression damage immunity, not only would you lose all your protected state buffs, but because you have 50% more suppression your recovery is slower.
This means much of your gear, your innoculator config, and your play style has to change since they removed that synergy with the protected state buffs.
Is it really worth investing in the Suppression skill tree if you lose all the benefits the moment you drop out of protected state, or would it be better to invest them elsewhere. In case you need a hint the answer is no, the suppression skill tree is probably pointless.

By changing this perk they've come pretty close to completely nerfing these types of "Protected State" builds. Maybe there's a way to still use the suppression skill tree effectively, but I don't care to find it.
I'm not going to reroll large amounts of my gear and find an alternate ranged crusader build, just because they changed the crucial perk that made the build work.
I'll either reroll a new a character, or <gasp>, play a different game.