Outside Limit Breaks, no Melee has to root themselves to be 100% effective; Part of their design is to be mobile to be most effective.

That's why Casters get a free sprint. Given the way Location is pinged, Casters need that extra bit of move speed on demand because, in most cases, if you're casting when the Boss begins casting their ability, you're likely going to get hit. You either use Sprint to get out in time, or you move ahead of time, in both scenarios you lose DPS time.

Once Melee gets their damage adjusted accordingly and Ranged get a slightly higher priority on Boss abilities, the need for Caster Sprint only becomes more apparent while the need for a free PDPS sprint will only be because of PvP.