My sage has around 1350 expertise and I still get rocked for 6-7k smashes and that's just the state of that class right now - they are going to hit and hit hard. I'm full balance and I don't find it difficult to perform well in PuG warzones (99% of how I play). The key is understanding your role and filling the role effectively - for example, without help, 2+ people focusing me means I will die and there is nothing I can really do about it. I can only hope to disrupt some objective before I die. The way to survive is movement and positioning - experience will teach you where to stand and not stand (which is pretty obvious to most, but takes practice to constantly do well).
Please, please, please understand that you're a support class, especially as a hybrid healer. You excel at controlling the enemy - force lift, force slow, stun, etc. If you're interested, I can post some videos of how I play (I don't pretend to be the best, but I'm not bad).
Kind of annoying they can run around wacking us for 6-7k tbh. I think sage overall needs quite an overhaul, we were a really competitive class at launch now we are sub par are at pretty much everything. And it takes substantially more effort and is a lot harder and more complex than other classes (glaring at smash derp).
Thanks for the advice though, I do try and manage LOS sometimes it's more difficult especially when you get a bad team and they let all the dps guys beat on me while I'm trying to heal lol. It has made it quite a lot better using the exploding bubbles though to be honest, running away and staying alive those few seconds longer to get an extra heal really helps.
I also have more expertise now 1.1k, which is helping but I'm losing quite a lot of HP and power Vs. my PVE gear, I guess I need some willpower\endurance augments, I'm also trying to stack power now since I've hit 30% crit rate and 75% surge.