Tip: Don't go Quas Exort.
It's bad.
But Exort Quas is one of the strongest ways to play Invoker how can you say it's bad?
You have heavy teamfight nukes, strong ganking abilities and as long as you have 1 point in wex you still have reliable disables and escapes. Cold snap is still effective at lower levels of quas, deafening blast is the same distance at all levels and the disarm length isn't the most important part of it, forged spirits are dangerous when you drop them on a support hero, and the only other spells that really suffer are the EMP/Tornado combo.
In the right hands you're going to melt faces while being one of the strongest heroes at every part of the game. You also make up for your miserable base damage with the exort bonuses, so you can trade hits more effectively.
EMP/Tornado is still good against the right heroes but you end up with a smaller effective spell pool for damage when you have low levels in exort.