Howdy. I'm currently GMing a mid-high level (11-15) campaign right now. This is my first ever campaign at these levels (I've GMed a few low to mid low games) and I hit a rock patch that I can't seem to work around and I'm turning to the pathfinder community for advice. So here is the story:
I have a game with my roommates that consist of three players, a Warpriest (ACG), Arcanist (ACG as well), and a vanilla Rogue. The other night they just killed a boss fight and after the Arcanist player voiced his opinion about it after the fact that he felt his character didn't shine in the fight. What this means is that the boss had high SR and stats were he was resisting a lot of the spellcaster's power. Our rogue however was the main damage dealer and torn into the boss with her sneak attacks and the like. The Arcanist player told me that he and the Warpriest felt that the rogue has become overpowered (which was interesting because the Arcanist was originally the overpowered one earlier in the campaign when the characters where mid-low levels) and this has made the game for the others not fun anymore because the cannot do as much damage as the rogue.
I expected this because I know our party's abilities (not their actual ability power but what the players themselves are capable of) pretty well. The Rogue specifically made herself the assassin, high damage output but weak in other areas. I geared the encounter best to all their abilities as I could. The Arcanist and Warpriest did really well before the boss fight with his henchmen and I thought they were out shinning the Rogue. The Rogue just happened to work best against the boss because she could focus her hits with flanks and sneak attacks. This made the others feel less glamours in the main battle.
So I guess my question to everyone is this: How do I resolve this issue? It seems that no matter what I do, someone feels under accomplished in my campaign. I've tried going over rules and strategies to even it out but nothing is working. Help me out people of the gaming community!