I would suggest picking up a skill-oriented character, ideally an archery-based ranger.
The archer ranger works well since:
- Archery does quite a bit of damage while being very simple to run. Since he's a few levels below you guys a well-built archer will be a strong contributor without outshining the Inquisitor in terms of damage.
- Archery would keep the ranger out of harm's way, which is ideal considering he'll lower level and much squishier than the other party combatants.
- The ranger can wield wands of Cure Light Wounds and do decent out of combat healing.
- The ranger gets plenty of skill points to play with and has perception as a class skill.
What is the sorceress good at? Buffs? Battlefield control? Blasting? If you lack buffs, get an archery-based bard. If you lack battlefield control, perhaps a druid. A switch-hitter ranger could help with skills, damage output and melee. An alchemist could also be cool.
@Dazaras - if the cohort were at the same level as the rest of the party I'd say a switch-hitter would be great. But a cohort with a low AC and fewer HP than everyone else is going to find melee combat a dangerous proposition.
The archery bard I think would be a good idea as well, although I tend to think of bards as RP heavy and so better suited to being a PC rather than a cohort. Maybe make him an arcane duelist (to make him more combat effective in place of bardic knowledge and well-versed)? The bard also shares the other nice feature of having Cure Light Wounds on his spell list.
Yeah, it sounds like an archery-based bard is your best bet, imho. I disagree that bards are more RP heavy than any other class, although you can definitely get into the RP with them. The bard can cover any skills your group is missing, while simultaneously buffing you and peppering the baddies with arrows when buffs aren't needed.
Here's a great guide to bards if you need it by Treantmonk
Bard or cleric, the buffing type.
Wizards are nice too but they are squishy even at full level, being lower level, with less wealth and worse stats would make for a dead wizard.
Archer rangers are good, but there are quite a few dice to roll, make sure you have all bonus calculated in advance or you will slow down the game too much. Also, you may want to consider a companion-less variant if you want to game to keep running smoothly.
My main suggestion is still cleric: can cast great buffs, can heal, makes sense from a roleplaying perspective since you are an inquisitor, is fast to play and does not steal the spotlight from anyone.