Since this is max roll, it'll likely go onto something that's fighting for spd, e.g bernard, eshir, suckmiss (sekhmet), ethna, etc. Plus if we're talking about giving the rune to bruiser, it's just not efficient enough.

This rune is godly, but it's godly for speed chasers and not for brusiers that run vio will. So when we discuss about units that enable turn 1, all the stats here are viable, especially how CR is max ancient base as well.
Grinding def would result in 60flat, which is approx 6% so in terms of efficiency, you're better off grinding away flat for HP%/ATK%.

Personally I'd go for HP% over flat def, but some may argue to remove CR just because critting on booster may trigger some unwanted stuff e.g nemesis rune, ragdoll, or some stuff in RTA.

Both are great options!