Grymkin is incredibly diverse as well and lock dependent so hard to say.
Having now played about a dozen games into them (three different opponents of varying pilot levels) the following seems worth noting....
They are incredibly potent against really all kinds of infantry. Sprays for days and then the alchemist are dirt cheap cloud and stationary bots. For example, Pigmen would HATE to see those guys across the table - since they THRIVE on the ability to ice cage multiple modles that are B2B followed up by a Supressor doing the Ice cage THang.
THe Vulcan is one(if not The) best Huge based models in the game. I think an important question for Grymkin is what is your strategy against that thing
Murdercrows (if you for some reason go infantry based) would have a roll taking out the support. Once Little Alyce, the rockets and Prospero go down you will have an easiler time of it. I would put them in the upper third of factions in respect to their desire for support. They can work fine without it but WITH in they really shine.
I would have to think hard about Arcana here and how best to really leverage them. I am not sure they are as vulnerable as some things.
Sacrifice might have a place in a good arcana build but would have to think a bit more about this. With the Sprays and the AOEs I could see an opportunity to really tilt back the attrition by playing that.
Finally I wonder about the Wanderer. Have to think more about this but OTHER than Ice cages (and those are really good so be aware of them) they don't have a HUGE amount of Def fixers outside of Prospo's leadership for the jacks. I wonder _IF_ (but is is mostly wondering) whether Starcrossed could not be leveraged for good effect and with the spray you could get your beasts into his grill to do their thing. But that also seems incredibly risky as he can ignore FoW with all the sprays and blasts and ice cages just must be removed ASAP to actually have fun with that synergy.