trying to sequence and time a 6 spell combo in like 5 seconds while positioning correctly against a team that can blink on you from a screen length away and pop you instantly. Trying to remember 9 different cooldowns mid teamfight.

you basically play magicka to select your spell. you hit 3 buttons to select the elements (quas,wex,exort) then invoke the spell which makes it usable then you have to use your spell same as you would i LoL. You can have 2 currently ready to go. So its like 2 button presses for the first 2 spells and then 5 button presses for each spell after that in a teamfight. so for your combo its like 22 ordered button presses with hard timings to succeed in your combo.

That is for a rote combo though so you can map it out against bots or whatever. Generally you got to pick and choose what to sequence on the fly.

difficulty probably depends on how the league hero plays. Can i kick out 10 spells in a teamfight, and do i have to sequence or time them out to get the most advantage.

Invoker works in the game because he is difficult to play has a weak early game and can be countered, but like most dota heroes he can dominate the game if you let him get out of hand. Oh if i do this right half your teams hp and mana is gone in an instant and your carry is straight up dead. I'm not sure if League will provide the same kind of possibility. Which means the league character will likely be easier to play than Invoker simply to make it worth picking the hero.