I mean you can literally say the same thing about any of the other casters and they don't have Ley lines weighing them down. When I play Summoner or Red Mage in raid, I'm not doing much in the way of moving either and my healers are normally just telling me to stay put and keep casting if the mechanic requires significant movement. When I healed the first Eden raids I just accepted that our strategies needed to be a bit different because a BLM was in the party. That's not Toxic gameplay. It's different gameplay that requires a different mindset from teams and healers. Not staying near a Black Mage's Ley lines isn't a difficult thing, hell its normally a thing to give at least a little bit of space to any caster or healer when you know AOE's are coming up, and the same is true for Melee's as well. As for the stacking part, thats actually pretty easy to handle, just stack on the Black Mage (or any other person with a stack AOE that does not have much free movement). Of all the jobs in a party, no one loses more by dropping casts. Move the AOE to them (if they are a good black Mage they should be just within range to where a melee can still hit the boss and stack) and then move away once it's over and everyone is healed back up.

Cooperation goes both ways of course. Black Mages are not like they were in 2.0 and have tons of movement abilities. I routinely will Aetherial Manipulation to my healers side sometimes for a stack Mechanic then instantly between the lines to get back to Ley lines if I put them in a place that is out of Melee range, and if triple cast is available you can sure as hell bet it's already marked for the heaviest upcoming movement mechanic. And I'm sure not all BLM's do that. But we shouldn't be making changes and decisions on class play based on the worst players, thats how jobs like Bard lose all their popularity and identity in the sake of balance and ease of use. BLM is literally one of the best designed jobs in the game. I'm more worried of what 6.0 will change on an already near perfect play style.