I can't really help out without logs or a video of you playing i'm afraid. I just had a look at your armoury, your mastery is really high compared to your haste, though i'm not sure if those are just your stat weights now according to simcraft.
armory takes into account the +3000 mastery buff, so he actualy have 2000 more haste than mastery...
you should REAAALY pay 1500 justice point to upgrade your weapon (go farm heroics/bgs asap if you don't have them), it's easilly a 1k5 dps increase, and whenever you get a weapon you think you'll keep more than ~3 timers, spend 1500 valor point in it to upgrade it.
Finally garalon is an awfull fight to compare dps. You should ideally focus boss and totally ignore legs and let melee cleave them (or sp/moonkin/mages dot them), as that is what benefits the raid dps most. If he has a higher dps percentage than you on the legs then you really shouldn't look at his dps. Try to look at fight like feng, spirit king, elegon, zorlok, tayak, emperess, protector (assuming no cl-cleave), lei shi or sha (if you're always in the same "group"), which are a lot less "gimicky" and on which "dps" is a relevant mesure.
as for "advises", read the sticky, use all your cds as many time as possible, and if you have a warrior make sure that you always cast ascendance with his skull banner. Can't help much more without logs
edit: did not paid attention the first time, but you should try to put as much "intellect" as possible on your gems : most of the case it's worth respecting gem bonuses, but red slot must always be +160intel, yellow +80intel/+160haste (or mastery or crit) and blue must be +80intel/+160spirit, and prismatic are +160intel
- regem chest, belt, legs, boots as mentioned
- grind the justice to upgrade at least weapon and alchemist stone
- change spellthread to the one with spirit
- change feet enchant to mastery
- reforge gear for hitcap accordingly
check your logs yourself:
- you general uptime must be very high - every caster has to remember ABC - Always Be Casting
- flame shock uptime must be very high
- lava burst should never ever land as non-crit as a result of that
- ascendance used on cooldown (within reason, burn phases change that etc) - aligning CDs does not mean let it sit unused for 60s
- try changing Blast for Elementarist - less complicated rotation, very tiny dps difference, earth elemental gives you a 60s damage reduce if you need it - lots and lots of parses in top 200 use PE
you should never gem a pure stat other than intellect as previoulsy mentioned, and at this point in the game there is no reason you should have an unupgraded blue. Gem slot bonus only needs to be hit if its more than 60 int.