Most brutal hunter build I ever came up with was a Halfling hunter, built to be mounted. Wild Child Brawler Dip so you don't have to waste points in Int, unless you roll stats and can afford it.
Take a wolf for the first 3 levels, as it has a free trip on the bite, and starts medium to ride.
After level 4, you change to a small cat advanced to medium size, so still riding.
Mount gets Bodyguard archetype, so he gets those feats without the Int problem.
Have Combat Reflexes, Weapon Finesse on pet to start, Bodyguard later.
Expertise and Pack Flanking, OutFlank, Lookout, and Escape Route by level 5.
AC has 5+ AoOs/round. You get +4 AC if they swing at you. You can move anywhere while mounted, with no AoO's for you and mount because of Escape Route. You count as flanking while mounted, with Pack Flanking, which bumps all attacks for you and mount by +4 while you are mounted.
This combined with a good Acrobatics makes Expertise to bump AC viable, as the bonuses you have from the teamwork make it all worthwhile.
Bodyguard gets to always act in surprise round, so you both always act regardless of perception, and most of the time (wis based caster with perception bonuses) you should get a full round in surprise rounds from Lookout.
Later, take Tandem Trip so that AC gets to roll twice and take better for the free trip on a bite, with all the teamwork stacks you should have a decent shot for as long as grounded opponents matter.
You can switch to a Roc later when flying becomes necessary, and everything still works.
You will want Imp Share Spells teamwork feat later since Bodyguard gives that up, and then buffing takes less time since you share the duration to both of you with a single casting.
Pet stays medium for land based, so never have the problems with squeezing mounts are notorious for.