Barst, Gordin & Odin

Barst and Gordin are good, although you might want to switch the Attack +3 seal with Speed +3 Seal.

For Odin.. I'm not sure, honestly. His defense and resistance aren't really high, even with Distant Defense. Blue tome breaker is..interesting. Was this for Brave Lyn and Reinhardt specifically, or for Brave Lyn and any blue tome units, because B Tome Breaker won't really help against Rein. His speed isn't really high, and he automatically doubles thanks to Dire Thunder.

Maybe it'll work? I dunno.

I don't have opinion about Odin and Gordin, but Barst looks, except for the Silver Axe+, there's a lot of better weapon to use.

The picture below is my Barst, this guy have saved my a lot of times on TT and in the last GC he have survived against a lot of enemies in the Lunatic(btw, WoM helps a lot on GC).
Don't look at the Deflect Magic there no special reason to Barst be equipped with this Seal =P