Another tip is to switch the last tier talent to Stay of Execution. Maybe pop GoAK a bit before, get 2-3 heals out with it (to get haste buff) pop all other CDs, then pre-cast Divine Light before breath. If you got HP saved up just throw EF on him and then Stay of Execution. Do NOT refresh EF until it runs out! Put EF on other raid members instead. Even if you can get a 1-2 HP EF going on another raid member, if it's buffed, don't refresh it. After that, either spam the boss with Divine Lights, or heal the raid with Holy Light for 100% transfer through Beacon. You can actually help heal the raid quite a bit through your beacon and Holy Light. Just store up some HP and use the EF priority Tsulong > Tanks > Anybody else. Buffed EFs should never be refreshed, just let them run out then re-cast it.
And keep track of your trinket procs, make sure they're up when you take a beam for bigger heals/more regen.
Concerning reforging, with careful timing you could probably just stick with Mastery > Haste, and drop Crit completely, it's crap. But if you feel that you need faster heals, reforge a bit to haste. The first haste plateu of EF is at 15.01%, next is at 25.03%. Generally they're not worth going for, you should aim for Mastery for big absorbs.
Haven't killed HC Tsulong myself yet, we're still working on MSV and HoF HCs, but this is just my 5 cent, based on how I do it on normal and I usually get really nice burst in on him.