Rate my H!Henry

That's a very unique H!Henry, though I'd recommend Vengeful Fighter over Desperation with a build like this since Gronnowl doesn't have that much power as well. You could also alternatively consider building him like Nino with Gronnblade, since he has access to +6 atk/spd from hone armor.

Pretty good! One thing to note is that since he's a ranged unit, dragon units are going to target his low defense instead. I find it's better to try to balance out DEF/RES on ranged units.

Also, Gronnowl seems more like a defensive weapon, rather than a player-phase weapon like you've got him built as, have you considered a Gronnblade build?

Still a solid build regardless!

You should really swap from Gronnowl to either Gronnblade or Monster Tome imo, probable Blade. Gronnowl is best for Enemy Phase, while Desperation is purely Player Phase. Fortress Res feels awkward, because it's lowering your attack on a set that feels like it's trying to be purely Offensive. It's not a terrible build, essentially, but it's trying to do too many things at once and therefore being not as good at all of them.

---
Here's my recommendations for if you want him offensive:
- Change Gronnowl to Gronnblade (if on an armor team), Gronnraven, or his natural Tome (if on some non-buffing team)
- Change Glacies to Iceberg, Glimmer, or Moonbow (Glim or Moon for Gronblade, because of the lengthened cooldown), so that you can procure your special more often
- Change Fort Res seal to something good in player phase (Atk+1)

---
If you want him to be defensive:
- Swap from Desperation to Vengeful Fighter, Quick Riposte, Guard 3, or some more useful defensive B-Slot skill (with QR in seal slot)
- Swap from Fortress Res to either QR-3 or Close/Distant Def 3.

---
If you want him to be mixed:
- Use either Gronnraven or Monster Tome
- Swap from Glacies to Iceberg for more Specials
- Swap from Fortress Res to Distant Def 3 (and all-around better seal)

8/10