Your big mistake is not making maindeck monsters for them :v
Sucks that the RUM cannot attach materials to a S.H.Ark. You may want to put a hard OPT to the GY effect just in case someone is bold enough to build a deck based on Summoning 3 WATER Xyz ASAP and milling 3 copies of this. 2 WATERs can be generated at once with Freezerdon --> Armored Crystal Zero Lancer.
Even if you send a WATER Xyz from the ED to the GY for Barian Servant's effect, AFAIK you won't be ale to revive it with the Bahamut since it still wasn't summoned properly, the "ignoring summoning conditions" only allows to bypass nomi clauses. Dunno if that was your intention, though.
Anyway, these look actually good enough. Darkraken Transporter is solid as a searcher. The Barian is nasty because it bring back regular Bahamut and further follow up with Toadally, etc. as long as enough marked MM Zones are provided, of course. IMO it outshines the Darkraken Bahamut. The ARK has an strong offense, and the protection makes it harder for the opponent to get rid of it. Overall, I feel the Bahamut and Depths Drake are the weakest of the set, although they do have their uses, the former for Rank-Up plays, and the latter for finishing games.
Actually, Barian and Bahamut can combo with each other to use the effect of regular Bahamut twice in the same turn:
1. Go for Barian
2. Revive a Bahamut Shark and attach
3. Summon Toadally #1 with Bahamut
4. Grab RUM Depth Force with Barian's gained effect
5. Rank-up regular Bahamut into Darkraken Bahamut with the RUM
6. If there is a target for DARK Bahamut in the GY, activate its detach effect to detach reg. Bahamut but Special Summon that same Bahamut anyway.
7. Use the gained effect of DARK Bahamut to attach a monster to reg. Bahamut
8. Summon Toadally #2 with reg. Bahamut.
Note that you would need some GY setup, and at least 3 marked MM Zones if you use Barian for a Link monster before dropping the 2nd Toadally.