The only thing I can thing of that clearly breaks ToS is account sharing. When it comes to content like Ultimate you need to have a full party and everyone should be pulling their weight, so obviously if you are unsure you can do it and prefer to get someone else (paid or not) they would have to access your character to do it. Of course the problem is there is no clear way of confirming whether a player is using another account unless there is clear proof. Some have suggested IP addresses, but if a person travels often but plays FFXIV on their laptop, it doesn't mean they are account sharing.