Also other then just stunning him a lot to avoid him being unkillable, play high mobility characters and be unpredictable (long range sucks when he can just charge you sooo avoid squishy snipers unless you have mobility like kinesa with transport)...
Do To Ruam's 75% resistance while charging, stacked on top of his potential 4000 soul armor from soul harvest, and 750 additional max health (from sinister allies) implies ruam can stay at a consistent 9250 to 16,187.5 hp... Sooo, Stun him ALOT....
Jenos should be higher in weakness list his relativity ability with his atral mark at max can out heal skye's base damage (unless she poison darts you then your screwed), and his void ability destroys her mobility allowing people to hit her.