From a scale I constructed a bit ago, where:

1. Trash (Pyxniel, Skull lord, Cillian, Shamrock) 
2. Situational (Opardin, Cybele, Ruel, Yoshi, Elegaius, Vergumkaar, Gurptuk, Harvest Jack)
3. Good (Sigmund, Versulf, Drokgul, Kantra)
4. Great (Karato, Tatura, Vlad, Roric, Hurndig, Astralon, Brago, Kreela, Rotos, Brakus, Foli)
5. Amazing (Brogni, Tormin, Maulie, Sir Nick)

I would probably rank Bivald as somewhere between 3 and 4. 

Have you rated all the legos?

I think some of those ratings are way off...

mind if i ask about your criteria here? i think you're pretty spot-on with bivald (personally i'd call him a solid 3, but it's a bit hard to this early), but wow, do i disagree with a lot of these.

Bear in mind that at the time I made the list, Hydra wasn't in my consideration list at all. That definitely would alter some of them. But, broadly speaking, I put especially high weight on usability in Arena, CB and DT Hard, which is why some champs may be higher than you would rank (Sir Nick, Roric, and Vlad for example).

So, for example, Rotos, who is largely useless outside of Arena, ranks as being Great. Same for Brakus, who is almost exclusively an arena champ (although he's on my CB team now!)

Also, if the champ does something that many epic champs can mostly do as well, I tend to rank them lower.

Curious which ones you disagree most about?

well as of this comment, what i disagree with most is the idea that rotos is mostly useless outside of arena. he doesn't bring much to a cb team, true, but he's pretty solid everywhere else. i'd certainly consider him amazing if we're also putting maulie and sir nick there.

going back to the rest of your list, i'd say pyxniel is certainly trash and i'll give shamrock a pass if you're going based on him at the time of fusion rather than post-buff (otherwise i'd put him no lower than good), but cillian and var-gall both deserve situational. cillian certainly is one of the worse champions to be offered up, but i'd consider him to be more useful than several champions you ranked above him (opardin, pre-hydra ruel). as for var-gall, he is pretty situational, but he's an absolute beast in those situations, particularly high level dt.

from the situational champions, i'd be tempted to push opardin down to trash-tier, and both yoshi and harvest jack provide enough value to be brought up to good imo.

kantra is honestly the one that brought up the most questions for me. i'd call her a pretty strong candidate for trash as well. maybe she's useful in a few areas i've not tried her in, but i have trouble imagining her to rate higher than situational.

past that, i'd say it's largely a matter of personal experience and taste more than objective value. that said, i'd push rotos and possibly hurndig up to amazing tier and there are a few i don't think i'd rank roric, brakus, and maybe astralon higher than good.

Agree with all. Except kantra, amazing champ before hydra. And I think can be awesome in hydra. 

Have you actually used her in Hydra yet? Mine is sitting in the Vault, collecting calluses on her rear, waiting for something to do... 

Bear in mind that at the time I made the list, Hydra wasn't in my consideration list at all. That definitely would alter some of them. But, broadly speaking, I put especially high weight on usability in Arena, CB and DT Hard, which is why some champs may be higher than you would rank (Sir Nick, Roric, and Vlad for example).

So, for example, Rotos, who is largely useless outside of Arena, ranks as being Great. Same for Brakus, who is almost exclusively an arena champ (although he's on my CB team now!)

Also, if the champ does something that many epic champs can mostly do as well, I tend to rank them lower.

Curious which ones you disagree most about?

Yoshi I'd move up to a 4 based on how well he shuts down all the toxic slow teams in Arena, especially Nehkret and Krisk teams.

Kantra down to 2 easily, as while her fusion was easy, random debuffs stink. I need to KNOW what my champs are going to do, I already have to deal with Accuracy-Resist checks, block debuffs and weak hits. Add in "this champ will do SOMETHING" and I'm using someone else always, thank you.

Roric down, his use is extremely situational. Impossible to tune well in Clan Boss, and slot in spider can be covered pretty well by Scyl, who everyone gets.

Hurndig to a 5. He fits into any team you want to dungeon run faster, and he is effective at two major rolls, debuff and damage. In Hard DT, multiple rolls can really matter.

Vergumkaar to 1. Faction Wars or nothing for the pine cone slug. And his slot is better served in my teams by a Haruspex.

Bivald is likely a 3.... I think. It seems like he has a well built kit that could do some fun things.... If Hydra ends up getting provoke based mechanics with the new hreads, which many in my circles are expecting to see, he will shoot up to a 4 or 5 really quickly.