I dont think the op wanted options that didnt involve the Roc companion and from what ive read hes not looking for optiomized damage, just to stay on par with grp. I think since your dm has okd the sorc/monk/fighter build to go with that as it gets you pretty much everything u want... Still suggest to look into the guided weapon enchantment with the bow though and loose the str score, uping dex to 13 for deadly aim and giving either ur con or wisdom and addtional bump..
Mr Whos: His primary source of damage will be the arrows themselves. For spells for the Imbue Arrow he will be mostly focusing on effects rather than more damage. If you see his damage output that I posted you can see that he should be able to put out a good amount.
I did consider Magus though, and it wouldn't be bad. It also wouldn't get all the feats that this build does and wouldn't cover the bases my son is interested in. Also, using Magus would be a more MAD build.
Guided is a good suggestion. I don't know if I would want to drop Str for it though especially as it wouldn't be a viable option until mid levels when he could afford it. With Wis and Str being his only real stats to focus on I think Guided is perhaps less needed for this build. Still a decent suggestion though. Thanx! :)