This ^
Normal attacks in FFXIV are NOT meant to be spammed, they have different effects like all the other abilities so there's no point in spamming them and there's no point in an auto attack feature.
You absolutely don't have to spam normal attacks on NM, in several occasions you even have to stop dps, so what's the point? you want it so you can chat during guildleves? pretty lame.
Basically if you want an auto attack feature you want a dot and, guess what, you already have plenty of them :O cast poison, dia, bio, drown or whatever you want, so you can keep chatting >.>