In gathering swirling shadows last night, I found a way to help prevent interrupts. The island with the shadow mobs in Twilight doesn't really have a nice corner to back into for casting while tanking a train. I found out that I could Vinelash cascade the entire train, then back out of melee range and still be able to damage the pack with my PBAoE spells. It broke the root often, but with mobs that have so few HP, one AoE is all you really need.

Interesting. It'll depend on the size of the mobs' melee ranges, though. There has been a trend toward larger mobs over the years, and larger mobs usually have larger melee ranges.

For that specific island, there's a spot up against a rock that works well enough as a corner to channel spells in.