Yes. Invoker is probably about 5-8 tiers "worse" than LoN, so it's not like it's complete crap... it's just that LoN is better on the higher end. I believe there was a GR89 clear in S5 with Invoker, so 90+ is still very much possible, maybe even 95+.
Invoker 2pc was both buffed and nerfed, which should make it overall more powerful and less reliant on the perfect high density rift to even get to over 25 stacks. At 25 stacks you will now hit 875% increase, previously you needed at least 35 stacks to get to this value, so any time you were below 35 stacks, you will now be stronger than in S5.
On top of that you get the 6pc buff for single target damage, and Akkarats Champion scaling adjustments, which should make pure invoker generally more powerful in S6, IMHO.
for some reason i cant get my stacks to go above 15 for invokers....it seems its capped at 15 instead of 25....atleast on xbone....id post it as a bug on the forums but for some reason or another it wont let me post on those forums...something about having to have a character....and not being able to link accounts anymore.....but anyways....its probably a bug for xbone....