For everyone saying that TOP being clearable without healers isn't a big deal.

Back in ARR for a very short period of time Summoner Titan-Egi was able to co-tank Leviathan making it possible to replace a tank with a summoner (I can't remember if 2 summoners worked.)
This was considered such a problem that it was patched I'm pretty sure within a week after it was discovered because it messed with the trinty balance.

Nowadays CBU3 doesn't care enough to buff the outgoing damage slightly of TOP to make healerless runs impossible.