Potential Male Morgan Build

Grima's Truth with Def+Res Smoke and seal Def/Res is akin to Sothe's Legendary dagger except that allies aren't buffed +5Def/Res and that enemies (excluding the target) are debuffed an extra -2 Def/Res.It is better to use Sothe,but if you don't have him (Why kill a perfectly good F!Grima?) ,then it is OK,I guess

I think you're headed in a good direction. Several things I would change:
- take a spd boon. We're seeing units with 45+ spd nowadays, sometimes before merges. You want to be able to initiate without getting doubled back. The extra def gets anulled by dropping his HP anyways. Instead of dropping HP, drop res and you will still end up with even defenses.
- use a sweep skill. If you hit your target once and it doesn't drop them into range for your teammate to one-round, you're probably dealing with a slow, super-bulky QR tank who's trying to charge some massive special against you. You can shut down one side of the spectrum (physical or magical) and at least deny some special charges against the other. I would probably take windsweep, because DC dragons usually use lightning breath which means they won't be able to charge a special if you don't double. (Non-lightning breath + aether also won't special you.) You can afford to take two hits of up to 45. Still probably not quite enough, but if a teammate has rally def/res then you have 48, which is probably enough against unmerged dragons without atk boons or buffs. Physical attackers are more likely to hit harder than that.

Sounds great, I have like 9 4* copies of him I've been planning on building if I don't use him for Spur Def/Res 3 fodder, but his Tome sounds interesting to me. I say go for it (when that Def Smoke seal comes out)