+def -spd Deidre

Close counter + QR3 + moonbow + (Def +3) Seal? You would have 22 Def, 47 attack, 35 res, 36 HP and 25 speed. If you give summoner support ( I think That's how is called) she would have 41HP,49 attack, 37 res, 24 Def and 27 speed. She would tank and kill a lot of units (And Dragons) with this build I think.

Your IVs aren't as bad as you think. I'd just go with a standard Fury ranged debuffer set. At least her attack and res are untouched, so she'll stay at a distance giving Spd/Atk-5 from a distance, only coming forward the once or twice per match that you need her to tank a blue or sometimes green mage.

Divine Naga
Reposition or whatever
Glacies (ridiculous burst damage, since she'll often get doubled and need to double back with QR due to her "good not great" atk stat. Glacies will be charged for the next engagement, to nuke even red units off the face of the planet, with like +30 dmg)
Fury 3
Quick Riposte 3
Speed Ploy 3
Atk Ploy 3 Seal

I don't recommend running her as some sort of CC physical tank, she doesn't have the physical bulk for it considering her speed is also mediocre (and yours has a BANE, at that). She'll get doubled and absolutely murdered by most meta physical attackers.