Learned many things on our last Odin/Alex attempt :
Odin/Alex/valks have very little regain, it was very easy to constantly reset their TP with 1 SMN, I even think 1 or 2 /smn could do it np. Not having to deal with all these TP moves and WSs make the fight 100 times easier to handle, we could survive the whole 60 min easily (or almost, we wiped after 51 min on a little mistake)
If only Odin is claimed, the valks will go passive for a brief moment after each Mewing Lullaby then automatically go attack Odin's target. This make things even more easier actually since valks are not acting 1/3 of the time.
It's impossible to detach a valk from Odin for a prolonged period.
Dark based sleeps works on valks!
Odin has a very high evasion like the valks and a massive auto-regen effect, it regen back to 100% instantly after a 5k BP. Dread Spikes (the only spell it cast) doesn't give it the regen.
We got down Alex to 89% then...

Was back to 100%, got it down to 89% once again and it did it again.
My conclusion is that the valks must be killed in order to suppress/weaken the auto-regen and/or Gospel of the Lost.