Slarks ulti is pretty "unbalanced" as of now. You get 4 seconds of free mass HP regen, you can't be targeted by any spell or hit by auto-attacks. Sentries, gem or dust works to detect your scaly ass. He basically gets 4 seconds that he can bash on you and all you can do is run or tank it and do nothing with it. The 65 sec cooldown is pretty long but you'll have it every fight basically, ofc. he can easily be countered by a Bloodseeker, which is pretty effective. But late-game if he is fat as fuck he can get 4 seconds to just bash you to death. I like playing him but I just think is ulti is too strong (the active), if they reduced his attack speed while he's inside it then I would find it more balanced.