I'm playing disc and absolutely love it. The blend of atonement heals and shadowmends/shields all while weaving in dps is phenomenal. If you're hating healing perhaps try a different healer. Also... Of course healing pugs is going to be a shit show, a lot of people don't care about mechanics and expect you to outheal it. I have a solution, stop healing them and let them die and carry on your dps/healer hybrid spec and kill the boss anyways. Don't encourage stupidity by healing people standing in shit.
In regards to burst healing players I feel like disc is in an amazing spot btw. Shadowmend + grace heal huge chunks with shields to stabilize damage. if you hate healing pugs then grp with 4 other friends/guildies and push harder content. It's a blast. I'm pumped for mythic+ this week!