What was already posted is true .... But...
God seeker is so much better than scyl.
I pulled godseeker late on, and never built her- i agree she looks great but i think scyl can excel in multiple areas and it really does depend on the situation.
I currently have scyl really fast and really tanky so that she fires off lots of passive heals and survives to pick anyone up, but i have also had her working quite nicely in a stun set in the past, she is just a great champ.
Barbarians were the first FW i completed because she was so awesome
Godseeker is quite impressive, although her base stats are kindof low for an epic defense champion I think.
Out of the list of champions you provided, I would say Scyl and Reliquary tender are the best of them. The other ones are conditional and/or not having as good a kit I think.
I really want Ursala or a Blind Seer... Im currently using Scyl and Aniri together in most stuff... My account is lacking many revive options sadly.
Overall, Scyl gets my vote too. AoE stun, 10% healing each round, decrease turn meter on A1 which also applies 30% slow, revive on a 4 turn CD with 50% ally protect, 30% increase speed on an ally randomly being thrown out, defensive tank that hits like a truck.
She has it all, and I've used her to even solo a lot of content by herself (such as Griffin). There is not one thing about her kit that I don't love, and she is a core member of pretty much all my teams.
With regards to Ursala, my biggest challenge with her is that her revive also applies a strengthen, which means that on auto she will always cast it even if no-one is dead. This can be good for increasing survivability sometimes, but it also means that the skill can be on CD when you need it the most.
For champions like Scyl that have a revive skill with no other benefit on it, they will always save it for when it is needed, which improves auto runs dramatically. Don't get my wrong, I love Ursala and she is on my main doom tower team, but it is an annoyance.