1. Depending on your kill strategy you often have to stop DPS on the main platform. See https://youtu.be/4gdv82b6jHM?t=8m28s at certain damage levels this makes the final push much easier.
2. WW can pool TeB stacks for the boat specifically. I top damage on the boat when sent over. Perhaps you're doing it wrong when you get sent over?
3. There are two "hard" parts to mythic maidens. The boat and the final burn. Everything else is nearly irrelevant.
Sending top damage over to the boat isn't a waste. Your damage on the platform looks great on the meters but doesn't really help you win the fight.
The boss while looking like a huge DPS race, really isn't that much of a DPS race. If you optimize way too much on cleave you're going to find awkward moments where you suddenly have to sit around and do nothing. Part of our strategy, but we sit around for like 45 seconds on Mythic doing nothing, which makes single target specs all the more powerful on the true part of the encounter (the last 20%).
Disc priests are much more powerful downstairs. Priests in general can shed penetrating shot, while other healers can't. Disc priests also don't have true throughput, where other healers can. Druids are absolutely amazing healers on boats, and depending on strategy you can have them do the first and third boat with HoTW.
3 Hunters, 1 Druid Healer and 1 Death Knight Tank (4th hunter on the boat that does not need a tank)