I know this isn't a CO board, but I'm pretty much on a crusade against the Cockatrice Knight's lvl 15 ability being too good, and to prevent myself from being a douchebag, I'm just doing the math on it. Before I get into it, I am against abilities that grant extra actions, especially that don't sacrifice your own actions and that combo with the very class that is intiating it.
I'm assuming 22 STR (16+2+4enhnc seems... relatively reasonable)
and a +4 Greatsword for simplicity. Seems reasonable WBL. no mount, charging for the 1st attack only.
Note that the average AC for a monster between 15-19CR that is not an ancient dragon is 30-32 with the horned devil being somewhat of an outlier at 35.
Their tohit will be: 15bab+6str+4mag+4Cockatricechallenge+2Actasone+2charge-3PA
so they're getting +30 on the charge and +28 on follow ups.
Lvl 15 first round charge and basics with X Cavaliers
1 cavalier, 1 charge:
Damage: 5d6challeng+2d6sword+9STR+4mag+9PA = 46.5 which is reasonable
2 cavaliers, 2 charges, 2 basics: 5d6chal+10d6chal+8d6sword+36str+16mag+27PA = 159.5 which is possibly OK at just 2 cavaliers
3 cavaliers, 3 charges, 6 basics: 5d6+10d6+15d6challenges +18d6sword+81str+36mag+81PA = 366 seems rather high.
4 cavs: 16attacks: 639 in one turn, lower on higher AC or DR.
So, I haven't counted being mounted and using a lance. And, remember, this is going to happen in the first round of every combat. Especially consider that I haven't counted the fact that it works on your lvl 15 animal companion who can potentially do a lot of damage acting individually unmounted (encouraging cavaliers to be unmounted is probably not the intention) I can also see 2 cavaliers in a group being something that would happen, and something that would be annoying, if I were a DM.
Now, I know a party of 4 cavaliers is probably not going to happen, but I am not a big fan of power creep, and just saying "it's not going to happen" is what starts it off being "oh, well you did it with the cavalier, so giving everyone actions in combat is OK." I don't really like Protect the Meek, either, but that does take actions from you later.
Correct me if I'm not abiding by niceness rules, or my math is off, or if you're going to change the ability anyway, or if you just don't like my face.