You can't assign anything to L1 as a warrior since you don't train any secondary skills for a second weapon/shield. At least, I've found no way to do it so if there is a way then the UI has failed me horribly. When I hold L1 nothing shows up on the move list either, so there's no default stuff that I saw. It's kind of boring not having many skills but the damage is pretty high so I just use the evasive slash and a downward strike for when enemies are stunned/fallen. Otherwise it's square ad naseum. . .
Can't you hold a shoulder button to do another 3 or 4 moves?
Fought my first gryphon yesterday and had it 3/4th dead when it. . .ran away. So dumb since it bucked me off in the air and I couldn't seem to clip its wings no matter how much I attacked there (not sure if it's even possible). Really wanted to kill it for the meat it drops and hopefully a feather to upgrade a piece of armor to 3-star. :\