The 'toxic' argument falls flat when you consider that whilst there's certainly problematic players in PvP you get just as many in PvE. Since the latter is a bigger part of the game, though, they wouldn't dare remove the chat from instanced duties. Imagine how horrible an experience it would be trying to get a group casual players through something like 3.0's final fight if you couldn't explain to those failing mechanics what the tactics involve? Imagine if, instead, you had the quick chat function as your only tool and every time someone died the only words in the chat were 'Nice job!'

It'd make more sense to just punish those who are caught out repeatedly engaging in toxic rants. If need be, they could hire more employees to deal with the reports. It costs money, certainly, though surely it could be funded through the Mog Station - or simply through getting more funding directly from Square Enix.