I've always put pre-TS Luffy at Veteran level even without Haki, so I never thought it was a prerequisite. He was probably >= Curiel level in Whitebeard's crew who was going toe to toe with Moriah.
But it's extremely difficult, if not impossible to go into High Tiers without using Haki.
But it's extremely difficult, if not impossible to go into High Tiers without using Haki.