Where are you experiencing party members dying in one shot? If it's in dailies, as a fellow healer, I notice people getting one-shotted most often in Krofin and Ashen. You will undoubtedly have to resurrect frequently, but in Ashen for instance, you can reduce the amount of damage taken by quickly purging debuffs such as Mass Bullseye, Mass Ruin, etc before they are hit with skills. The healer class has unfortunately become devalued over time, but in my experience, I still find the class very useful and rewarding to play. It's definitely more useful than simply Celest and Res; your heals are far superior to the Iss heal, purging debuffs, buffing Entire Resistance + Mass Mana Gain/Divine Prayer with Shield/Magic Shield skill enchant, recharging MP, debuffing bosses, and so forth. I'm sure you get the idea. Hope you don't give up on healing!