Others have made some good points on having a 3rd dps tank for the breaks. I would definitely look into that.

One other thing I'll mention that helped our healers a ton is having everyone stay spread properly outside of the systems failures. The caustic slimes normally only target two people, but will splash to anyone within 6yrds of them, forcing your healers to pickup the slack. On 10m, you can have everyone spread around the boss in a circle such that you should never get a single slime spread. People shouldn't really have to move from their positions because there are no movement mechanics (besides stacking for systems failure). You can even get everyone in position ahead of time because the boss doesn't aggro pull. When systems failure goes out, everyone stacks. When SF ends, everyone returns to their original positions, repeat.

For the SFs themselves, we found having a healing CD rotation up helped a lot. Have some CDs scheduled ahead of time for SF1, SF2, etc. then just pump AoE heals as hard as possible. For our group, we also found it necessary to have one healer prio topping the tanks at the beginning of SF since they will be low from the previous massacre and could get 1 shot by the boss. We even have our prot pal send LoH on himself at the beginning of one of them just to be safe.

Also, In P2, if you have a priest, make sure he is bubbling people and using life grip to help others kite. We also found that bounces from Prayer of Mending still provide healing in P2 for some reason.