When that LM u mention solo healed BfE T1, his grp was almost all dead as u cant spread the WL around efficiently enough for the inferno.
Outposts can be soloed by any class.
Most creeps can be soloed by any class as things stand atm. It all comes down to the player that cntrls the altar.
So my take in this is that if u compare LM to hnt u can say that he is OP due to WL. But if u compare him with champ and wrdn u will see no difference and WL wont be OP. Compare LM with the rest of classes and ull see WL gives him a slim advantage if any.