certain parts of this thread are becomming pretty ridiculous really
Lets see if we cant put a few of these dogs into a better light.
First of all, as I stated earlier aoo's are not incredibly common. As levels increase the number of ways to avoid them entirely increase dramatically. Even at low levels though they arent terribly common.
A way around this is the summoning trick. Even though the rules actually go against this I have no problem with it. In effect you have one party member burning a full round action plus a spell slot in order to give another character who has spent several feats a few extra attacks, assuming of course that some other factor does not interfere (such as the enemy having the same combo and useing it against you, one or both of the two characters being incapacitated in some way, or any number of other things). It simply sounds like good tactics to me but only useful to an extremely small subset of characters who are specialized to do just this.
Once again, this is a combo where you need two characters who both have a nice amount of resources dumped into it and all it does is give a few extra attacks. Going by useing a 3rd level spell (for d4+1 weak critters) this could grant up to a maximum of 5 bonus attacks for the fighter guy. If the mage gets his spell off, if he rolls maximum, if the fighter type gets a chance to attack these things with the aoo's, if the fighter has a pile of feats, if the fighter has a high dex, and if the fighter hits all of the guys (pretty likely for the summons). The third level spell could have instead been some other third level spell though and possibly done just as much, or summoned a 3rd level beasty who could provide flanking and some other abilities, take hits away from the party (psuedo healing), not require the fighter type guy to have the pile of feats, and it might wind up getting more than those 5 attacks anyway and it has a much lower chance of backfiring.
So, for that tactic if the characters are built in just the right way then sure, it might be useful when they are working together. Team work and tactics. But, even then, it is easier and sometimes better to simply use the spell in another way. Early on this is actually a sink in power, not a boost. Later on one can trade a lower level spell for a big effect, but it still takes quite a bit to get it going and working. That is still a big drawback.
There really isnt any problem here from a power perspective, it can be nice but other things tend to be much better.
Cleave works less and less as levels increase (creatures tend to take more and more hits to take down and have other evasive abilities along with needing to be within range of someone else to attack, not always easy) this is just a minor ability which hardly ever happens, but even when it does all it means is that this feat still grants some sort of a benefit. It is a sad day when people try to hinder a feat that already loses power so rapidly
Cleave is a strange feat, it is one of the few that work better for pcs than npcs. Still though, I havent seen many people take it, it is just too situational. Most of the time it is nicer to simply get another ability that will come up more often or can be better planned for. Which is better, the ability you can depend on to work and plan for it, or one which occasionally might give you a bonus but generally cannot be planned for (even the summon tactic can be very situational, sometimes even available space negates this tactic).