If you want to do Mythic+ Content, you need to be viable.
If you want to do Visions (you know, the thing this patch revolves around), you need to be viable and must be suitably expected to be able to survive and deal the damage necessary - even as a tank (which won’t help you - and you’re not full-clearing as a tank).
If you want to raid, you need to be viable.
Pick your poison.