Since you don’t have Seshat, I vote for Domitia. Besides, Grimble is a situational hero. Regarding the emblems, maybe this guide will help you in your decisions.
Then set your defense Triton, Kingston, Bold, Domitia and Musashi. But when you have the darts, go with Joon maxed and replace Musashi. Besides Joon has a nice costume and who knows…
Bold is a better tank. His skill is superior. More healing and the atk buff for all allies, is great indeed. His fighter class may prove very annoying. I saw him many times reviving 5 times in a row. And if he actually fires after a reviving, the opponent is screwed. Besides, Grazul is designed mostly offensive, being effective when the player controls her.
Grazul is not good as tank, also in any position defense. Because small heal and not punish opponent, only protect status ailment, but then attacker can delay their skill for 2 turn.
Boldtusk make all allies buff attack (big advantage for our slash and skill attack), heal more, and his class is fighter, he has chance to revive.
I was use him as tank and he can stay at Diamond Arena, but now I replace with Anzogh.
Although in a recent war, I faced a multi-emblemed Grazul tank with high level troops that took a bulldozer to take out. A lot does depend on the other heros in support too.
I have Bold Tusk with 18 emblems in flank, still on my defense team in diamond too.
As you can see I put some Emblems on several heroes already. I`ll write down how many levels I have achieved in the different talend grids and how many unused Emblems I still have:
Fighter: 6 levels and 136 Emblems left
Cleric: 7 levels and 61 Emblems left
Monk: 6 levels and 61 Emblems left
Paladin: 7 levels and 72 Emblems left
Ranger: 6 levels and 106 Emblems left
Wizard: 7 levels and 79 Emblems left
Sorcerer: 192 Emblems left
Barbarian: 4 levels and 35 Emblems left
Druid: 6 levels and 61 Emblems left
Rogue: 7 levels and 128 Emblems left