Dunno I haven't have had any issue with leyline beside the second part of E4S p1 where leyline would often coincide with a heavy mvm mech...
I also think it fits the job fantasy very well.
Each caster has its issue in term of movement
RDM has to go melee else they overcap (which I find more annoying than leyline sometime ) , smn wants to be static during Bahamut to avoid loosing peanut potency on ruin and BLM have their leyline every 90s .

If any change I wouldn't mind reducing the duration a bit (with some buff else where)

If the BLM you see do not want to move to do mech then they're just bad. And mana ward will hardly save you from an extra hit... I mean it's not like ff14 raid design is dodge or die...

I never had an issue being in range of healer (aka center of the map) and stay on my leyline on any fight...