The problem with Nagrand and Lordaeron right now is the shape of the pillars/tomb. Bear with me this is a LOS QQ.
Because these obstacles are circular, if the runner class and chaser class are moving at the same speed, it is possible to be out of LOS 100% of the time forever. The only way to break the pillar spin is to snare or stun the runner. I'd like to see future arenas move away from this circle shape to give LOS a 'cooldown'. LOS is a great feature and makes arena games fun, but it should be something you can only use once until you get to the next obstacle. Like you can jump off the bridge in BEM, but once you have jumped once and broken LOS, the other team has some time to catch up to you in the open until you get to the next obstacle (if the pillars weren't there).
Consider the following obstacle (viewed top-down, open space in the center)
The two corners can be used to break LOS from the other team once, but after the other team gets around the corner, you cannot continually run away from them like in Nagrand, instead to break LOS again you have to go back through them. You can still break LOS, just with a cooldown now.
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