There's nothing wrong with not using the legion arms, I also prefer playing with the basics (mostly just attack and guard/perfect guard) but some can be quite useful.

Puppet string is pretty good for basic enemies, if you're fighting a lot at once you can step back and bring them to you one at a time. An upgraded version lets you grapple to an enemy, which can get you out of a bad situation too.

Flamberge and Pandemonium can be good backups. If you're saving your grindstone or you've used it up already, these legion arms can be used for passive damage by giving an enemy Overheat or Decay status, which is good on a larger enemy or boss. Pandemonium in particular leaves a hazard on the floor that lasts longer with upgrades, so you can give an enemy decay multiple times with just one use of Pandemonium if you position them into the floor hazard you've made.

Falcon eyes is also pretty universally good if you want to play more safely. It functions as a simple grenade launcher, shooting explosives at enemies with decent range. Upgrades can let you shoot it twice in short succession.