I mean why not. They're different games within the same genre. I think it's simply positive if games within a genre evolve together and use similar stuff that works.

If you actually look at the skills and what they do, they're mostly different and unique to Invoker. Yeah, the spell-combining stuff has been "copied", but so was the 3-ability-plus-1-ultimate system. And a lot of other stuff. But it's still different enough to attract different player bases for different reasons, I don't really think that Dota + LoL compete for the same players a lot.