If you get to 65% during night phase and your dps are killing the adds before they get to boss then the only reason you can't kill the boss is underperforming healers.
The most important thing a healer can do besides healing is dispel terrorize immediately. DBM has a timer for it that begins after the Unstable Sha spawns.
Tsulong will still always take at least one tick of Terrorize (lots of damage) and this can be mitigated by using Hand of Purity on him before it goes out.
All your healers are underperforming but I'll focus on your holy paladin who can do a lot more than he currently is, here are some tips;
USE YOUR COOLDOWNS MORE YOU ONLY HAD ONE OR NO USE OF EACH CD!!! You can use GoaK, wings, and DF twice (use on first breath in first day phase, third braeth in second day phase - make sure they are used TOGETHER).
- Consider reforging to haste as most of your mastery is wasted on tsulong and mana is not an issue, especially when 3 healing.
- Beacon Tsulong as soon as day phase starts.
- Glyph Flash of Light, use it once right before each breath (see below).
- Spec Execution Sentence.
- Spec holy avenger and blanket 3hp EF on the raid at the very start of both day phases (after you beacon boss, before first breath).
- Each breath you want to do a similar cast sequence;
Holy Shock (chance to pre-load IoL), Flash of Light, GoaK+Wings+DF+Int pot(BREATH HITS), DL DL DL HS EF ES (BREATH ENDS).
The other healers can obviously improve but if your pally does all of that he can EASILY solo more than the required 15% per day phase to kill the boss.