Dragonslayer is one of those that does what the description suggests which is nice. In a dragon heavy campaign I think it is reasonable 17/20, in 90% of games its probably a 7/20 since most of the abilities don't translate. If its improved critical and Overcome Draconic Spell Resistance worked across the board or dragons plus all favored enemies or could be expanded somehow this thing would be ok as a 17/20.

As is I think it is closer to 12/20 just because the PRC is too focused.