I love the summoner class, but not because of the summons. I love the eidolon and think because of its build whateveritisyouareimagining mechanic it is one of the funnest classes in the game. That said I am less pleased with the summoner himself. While playing one I always feel lackluster, as though I am playing second fiddle to my pet. Now I am GMing a campaign and I have a player who has expressed similar concerns. So this is my proposed solution:
Get rid of the Summon Monster (sp) and replace it with Eldrich Blast (sp). Eldrich blast works like the warlock Eldrich blast of 3.5 except it can be used 5+(chr) times per day, and it increases in damage every third level instead of every other. The summoner is actually siphoning off some of the power of their bound minion, and thus must be within 30 feet of their eidolon to use this ability. Lastly because their eidolon is being taped as an energy source it isn't as powerful as otherwise might be (fewer evolution points). This eidolon has a perfectly linear evolution point growth starting at three and ending at 22, instead of 26.
With this change I envision a feat that increases the number of Eldrich blasts in a day, and the distance allowed between summoner and eidolon increasing at higher levels.
I feel this archetype is pretty balanced over all, and allows the character to participate in battle. I also think it is good because for this archetype charisma is no longer a minimal stat, and would be the focus of the class, as I feel it should be.
I know both the warlock and summoner are controversial, so combining the two will hardly be popular. That said does the archetype look mostly balanced? Have I made any glaring oversights? Constructive criticism is appreciated. Lambasting either the summoner or warlock as being broken/horrible/stupid isn't really what I'm looking for.
Well, for a start you need to think up a good name for the class. Also you might need to up the base damage: a 7d6 blast is puny for a 20th-level character.
I would call the archetype "Eidolonmancer," because story wise the summoner gets all of his power from his bound outsider/eidolon.
I am running Rise of the Runelords and so I'm not too worried about a capstone ability because the characters will only get to 18, I think. That said I was worried the damage would be too high if it was +1d6 every other level. Could you follow the warlock Eldrich blast progression and have it be balanced? I don't want it to be over powered, but since I've restricted the amount of uses per day does that balance things some?
Remember, blasting is generally the weakest option, especially at higher levels. Even a 3rd Edition wizard would have 18d4 hit points at 18th level (ignoring CON bonuses) which is an average of 45 HP. Even a 11d6 attack does an average of 38 HP damage (ignoring saving throws).