Pushback has always been the bane of spellcasters and Hunters everywhere, be it in PvP or PvE. The slightest bit of damage, even the environmental kind, can make a quick 1 second cast somehow stretch into eternity. However, as of the latest Beta build, the eternal cast time may be a thing of the past thanks to some new spell pushback rules.
When you're casting a spell, the first two hits will add .5 seconds each to the cast time. Every other cast will have no effect. For channeled spells, the first 2 hits will take 25% each off the total duration, while all subsequent hits will have no effect.
This sounds like it should be a pretty awesome change overall, especially for solo or small group PVE, where one who has drawn aggro or otherwise lost control of their target can rest assured that it will take them only a single second longer to get off a heal or cast a crowd control spell. Here's hoping this is one change that makes it to the live servers.
Of course, it's probably still worth taking that pushback protection talent if you can. There's no use tempting fate, and that 1 extra second can be a surprisingly long time when you're under pressure.
Thanks to everyone who pointed this out!