Who can use dull ranged (B) skill to good use

DC users are generally a good choice for that skill (unless you need that B slot for QR). There really aren't many ranged units that are going to get that much benefit from this skill since either
A. They are already built to be a sort of ranged tank and can take attacks fairly well from other ranged units with buffs anyway
or
B. They die as soon as you sneeze in their direction regardless of buffs so the skill would be wasted on them.

Due to this skill sharing the same slot with so many other good and generally more powerful skills it really is going to fit well on only a few units.

I’d say hold him for now. TT needs a bonus unit if you didn’t pull any other Branded King focus units. I snagged a +def-res MMorgan myself and am going to just use him in the TT sand then decide what to do. Probably AA him. Lol

My Effie w/Berkut’s lance, DC, and Distant Def would make GREAT use out of it... :))))

Dull Ranged, to me, feels better for supportive roles, though I could see this being a great counter for Blade Tome (like you said already), Magical Calvary, and Dragon users since it highlights the ability to counter mostly magic at this point and time. However, I feel like there are far better B skills for almost all units available. This feels out of place for someone like Morgan to have in his base kit too.

The biggest problem this has in the slot it's in, which I believe is B, so that is sacrificing a tremendous amount of different offensive options and take away a lot of protection some units need to function in general. There are too many godly B skills currently dominating the meta.

I think this skill is a heavy risk for a lot of units and I'm having a hard time of think who should use it myself.