Illidan is good in a 2x2 team (2 healer 2 tank/peeler) but in pugs he's quite often free food as the bad ones try and duke it out, get slapped hard as they jump in hyper aggressively and then blame the team etc... If you like Arthus do you already have stitches? Arthus got beaten to a pulp in the last round of nerfs and I mean totally butchered - less sustain, less damage, less ability to tank, it's horrible. Stitches on the other hand is still broken as hell and you can't even hook your own team mates by accident like dota - I would suggest holding out on arthus right now, he's just in a really bad place. ETC's kit is similar-ish to arthus and in a much better place if you want to initiate and tank for your teams.
I did notice this this morning. I was watching a video of Force playing Arthas from a couple of months ago, and the damage he was taking was non-existent! Totally different from when I was playing as him last night, he got slapped hard when I tried to run in with the AOE damage spell he's got.