Are you tried proper defence stats? i play even as engi and have no problem to kill multiple mobs same time, i was switch to my 5 runes alt and still i feeled tanky
try take at last 170-200 concetration and 150-250 bloodlost, that schold inaf, if you have more cs stat you can put caution to be even more tanky on 40% hp
another step is to max your dmg, so more heal will back to you per hit, or kit a mob, using slowdown/stun/knockback/dash/teleport
you no need also go for ai-rihat alone, ask husband/wife in game to duo ther or eventualy you can search for small squad up to 3ppl, and do daily quest togheter as team, if your not feel tanky, let more skilled/ or more sustain player first hit, then attack 2-3s after him, so you will not get any dmg at all, and your squad member will be your live shield, until you get more eq and you will can do it alone
i recomend to take 2dps (1 mele and 1 range) + sup
for exemple : Paladin, Mage, Engi
Engi drop -40% shield for Paladin and heal him
Paladin charge for many mobs he can (he also have 2 panic buttons to pt heal, and pt barrie if need)
Mage cast tear ability named Cataclism, or the new one
if any mob survived, engi nuke finish a job
but you no need use tear skills ofc, or if on cd, you just cait smaller number of mobs (despend from tanknes of your paladin, or how good engi sup managing his defensive resourses, it's up to you)
Another exemple : Demon, Bard, Engi
Engi drop -40% + heal demon
Demon use his -40% too, then change to range attack doing nasty dps and heal from bloodlost
And bard is just bard