That's pretty much how I see it, it just seems like a big jump to go from Cleave being limited to once per round (no matter how many people you kill), to Great Cleave having no limits on the number of uses (aside from the sheer practicality of how many people you're able to kill).
I'd never really thought of it before, because to be honest, I had forgotten Great Cleave could be used multiple times per round. (In my defense, I'm playing my first cleaver in awhile, and I haven't taken GC yet.) But combining Great Cleave with AoO's is potent because while your cleave attempts go off at the same attack bonus you strike with (so you secondary and tertiary attacks aren't as likely to hit), your AoO's always go off your highest BA. So let's say you make a guy with a Reach Weapon, Combat Reflexes, and with a good Dex (by mid to high level, probably 18 with stat enhancing items or buff spells). Ideal circumstances, a lot of provoking dire lemmings, and so on, you're looking at 7 possible Cleaves in a round (5 for AoO's and 2 normal attacks, for a character in the 6-10 range).
I don't think its unbalancing, especially compared to what the casters are doing and a comparable level, I'm just saying that its a drastic difference in effectiveness between having Cleave and getting 1 Cleave attempt per round, and taking one more feat with a low prereq and getting as many as 7 Cleave attempts per round. Most Feat trees don't have that kind of bump.
I'd never really thought of it before, because to be honest, I had forgotten Great Cleave could be used multiple times per round. (In my defense, I'm playing my first cleaver in awhile, and I haven't taken GC yet.) But combining Great Cleave with AoO's is potent because while your cleave attempts go off at the same attack bonus you strike with (so you secondary and tertiary attacks aren't as likely to hit), your AoO's always go off your highest BA. So let's say you make a guy with a Reach Weapon, Combat Reflexes, and with a good Dex (by mid to high level, probably 18 with stat enhancing items or buff spells). Ideal circumstances, a lot of provoking dire lemmings, and so on, you're looking at 7 possible Cleaves in a round (5 for AoO's and 2 normal attacks, for a character in the 6-10 range).
I don't think its unbalancing, especially compared to what the casters are doing and a comparable level, I'm just saying that its a drastic difference in effectiveness between having Cleave and getting 1 Cleave attempt per round, and taking one more feat with a low prereq and getting as many as 7 Cleave attempts per round. Most Feat trees don't have that kind of bump.