Why run with that much haste? Softcap is 1269 (38.7%), thats Unbuffed, then a further 8.15% is gained from raid buffs. You are seriously just over gemming haste and not balancing other stats.
Gemming for me was balancing a good ammount of haste but compensating fro low MP5 and Spell power gains, i have matched all my gem sockets while keeping a good balance on all. And im a MT healer and when needed i spam raid with CH.
Since 3.3 i have changed from using Riptide>LHW to LHW>Riptide for oh s**t moments, but Riptide>HW with 2 set bonus is just insane, 1 second casts on Healing Wave on the tank at 6 second intervals. Healing wave is still an under used heal from us, but thats NOT all the shamans fault, this is more to do with Raid Leaders still using shamans as raid healers, Druids and Holy Priests are still way out in front for this, Pala's & Shamans should be on MT's, and Disc using all abilitys on the whole raid. Shamans always ES the MT, and 99% spec into Healing Way 3/3 and this is a waste if your shaman is assigned to raid healing, so not only is the shaman loosing the bonus healing on ES hes also loosing the 25% extra healing from talents on the MT.
http://eu.wowarmory.com/character-sh...and&n=Zianator
Since 3.3 i have actually started to top Healing again along side Druids (Not that this is/was an achivement), but its a combination of how to heal, rather than the normal spam chain heal from the past. Mana not really an issue in how ive set my self up, most fights i finish around 20% mark.
haste is the biggest stat we can go for, but dont jsut gem for that, or your short commings in the bigger mana intensive/dmg fights will start to show.
Note: These are my personal views on it, and after a lot of research and mountains of gold spent on gems and stuff, i found this way to gem and heal a better solution.
And i totally agree with Comablack, get the 2 piece, then take the riptide totem before parts 3&4.