let me give you a rundown of certain skills first:
Charisma = CRAP it only affects rock paper scissors and people like you a little bit better but really it's just useless
Leadership = pretty good as far as i know and heard
Pickpocketing = useless at this moment you can easily get some gear with +pickpocket
lockpicking = most would say useless i'd say it's ok. you can either break chests using your weapons or spells. or lockpick them i personally prefer to take a point in it and use +lockpicking gear for the rest to lazy to bash chests
sneak = honestly don't know if this is usefull. but i my self don't think it is. invisibility is better imo
Crafting = deffinetly usefull but that water/air mage you mentioned gets free scientist talent giving him +1 in crafting and blacksmithing. so it's best if you give him +blacksmithing or +crafting gear and maybe put 1 or 2 points in. OR you could later unlock henchmen in a special place ^^ and you can make 1 your crafter and just leave him in that special place and get him every now and then

I haven't tried melee rogue my self. but i do have a archer and i can tell you ranged is pretty nice :P
your party is decent. i personally prefer to go pyro/air and then give the mage companion water/earth (damn the person who decided to make him air/water >.>)

my party setup is
1. Battlemage with sword/shield and pyro/witchcraft/aero/man at arms
2. Ranger wit marksman/bow/scoundrel ( 1 point for the invisibility and haste skill) /barter
3. companion water/earth/crafting (Almost completely ignoring his air part :P
4. companion two handed/man at arms/leadership/defences