Because of their inherent limitations of Summoner (namely the 45 second at minimum recast time on Bloodpact: Rages), it's hard for them to solo for Exp very well. That being said, several Grounds of Valor areas can be done fairly easy for a level 76 Summoner. For example, all pages, even just Page 1, of Kuftal Tunnel can net you exp all the way from 76 onward to 99, and the mobs for those early pages are easy for you to kill at level 76.
Alternatively, if you're looking for a more traditional way of soloing, you can do Imps in Caedarva Mire outside of the Azouph Isle Staging Point, which are T+ to a level 76 but easy to solo with some practice.
My thoughts and reviews
Lady Jinte wrote:
Vlorsutes' Negotiation Skill rises 0.2 points
Vlorsutes' Observant Parent Skill rises 0.3 points
Vlorsutes' Argument Diffusing Skill rises 0.1 points
on all sorts of sci-fi stuff...and things.