Had a thought for the 'single level dip' section. Dawnflower dervish (bard archetype) from Inner Sea Magic would make for a great single level dip. One level gets you dervish dance for free, so 2 feats gained there. In addition you get inspire courage at a total +2 attk/dmg bonus for yourself. At level 3 consider taking harmonic spell, by this time you have spellstrike and spell combat. The combination of which could be used to maintain a constant and free (go go arcane mark) +2 attk/dmg. True CHA is your dump stat, but since starting a battle dance is a move action, you still have your standard to cast a spell making even round 1 free.
This next part I'm not 100% sure works. I'm trying to figure out how Master Performer from the faction guide would interact. If the additional +1 is added in before its multiplied then you have a +4 to attk/dmg (gain of +2attk/dmg), making it a better combo than wpn focus and wpn spec (+1attk, +2 dmg). If it comes after the multiplication, then wpn focus and wpn spec are superior and master performer isn't really worth it.