I’ve been trying to figure this out, and after thinking it through, I think a non-Vampyr mayhem 4 build would have to be heavily gear based, and require 2 key things:
You need minimum the following:
You need a Bloodletter with health regen
You need a relic that removes 75% health (+ health regen here too)
Recharger or Stop Gap
Transfusion grenade for shield
Red Tree things, but stay above health gate
Auto Bear
Dakka bear
Green Tree things
This is my well-tested strategy and I think it can be quite strong
Shoot things
On shield break, throw transfusion grenades
When this fails, jump into IB for shield regens
Once exited IB and shield breaks again, jump into dakka bear for safety time
After IB dies, throw lots of grenades
Respawn
Super simple build, honestly. Been using it for a little while and not crying too much.
edit: this is partly theory craft and partly tongue - in - cheek
My favourite mayhem 4 build is a 1hp build with a Blast Master com. I cleared Slaughter Star first time with it and can cruise through a lot of mobbing. I despise the Shaft so haven’t tried it there and my build fails under the Takedown’s heavy fire.
The keys to my survival are a Big Boom Blaster, a Deathless and self dotting.
The 20k shield I have gives the big boom plenty of time to drop boosters. Against CoV the self dotting is important as I want as many hits as possible to proc boosters. So if I get hit by a rocket that drops me to 600 shield, I can take cover and use a self dot to proc a booster or two.
I technically have 1 point in Vampyr but the point is redundant as it can’t heal my 1hp and I’m not wearing a Bloodletter.
Kyb’s Worth is my main gun, I have two. 1 is fire/cryo the other shock/corrosive, they’re my mob killers. I keep cutsman and recursions for certain enemies, but since getting better Kyb’s I’m barely using them.
I feel like the whole world is going to know I use Kyb’s soon with the way I never stop shouting about them.
Minus the transfusion grenades, I’ve been doing precisely all of this with both the Bloodletter and the Blast Master COMs and it can suffice in most areas, but it’s not seamless enough for a map like Midnight’s Cairn where you can get easily surrounded and the tougher enemies spam AOE attacks where Gearbox see fit to invalidate their own skill tree design and deplete your entire shield in 1 missile regardless of you going to the effort of boosting its capacity as much as possible. Out of all my testing, it seemed like the most effective way to make a lvl 50 stop gap work was using a Bloodletter and a Knife Drain relic (either or both with static health regen) with Tenacious Defense doing 40% of the work and a Facepuncher clearing up the other 60%. It’s one way of doing it but that might be a little too finicky for some.