You seem fairly geared and you definately have a lot of experience, but some of your gearing choices confuse me. You don't appear to use a CSD meta which would be quite beneficial to you, although the slight int to SP scaling of the arcane tree leads me to realise what you're trying to do there - though statistically, I still believe the CSD is substantially better. I haven't checked this out since 3.2.2 Arcane buffs but with no changes to the intellect or critical strike rating scaling I can only presume it's all the same, if not moreso as CSD would add a percentage-based bonus to your (now larger) crits than your current gem's flat SP bonus (well, slight scaling with int, but I wouldn't really call that scaling).
Gemming 10stats may seem like a nice investment but what can you honestly say you get from this? In terms of DPS, 1.725 spellpower from the intellect and 5.5 critical strike rating from the spirit. To add that the only other real bonus is a 100 health increase, that may be nice to have, but can you honestly say it's worth losing the 10.275 spellpower you would get from gemming 12sp/10spi instead? I mean, personally, I wouldn't have gone for the socketbonus at all there, but if you really had to - I just don't see the logic in your choice.
You're also gemming SP/int, pure int, and pure crit to match yellow sockets. With haste being 61% of the DPS increase of even spellpower (prebuff), and almost double the value of crit (crit being 52% as valuable as haste), there's no reason not to gem every yellow socket with SP/Haste. I'd also prefer to see a 50sp/20spi to 50sp/30stam on legs for the extra 11 crit, but if you feel the 300 health is a viable choice (which would be a fair call if you're raiding hardmoes such as firefighter or grand crusader valks - however I assume you aren't), then I guess I can accept that.
Also, your hit is WAY beyond what is needed as Arcane [8% Softcap, 11% Independant Cap compared to your 13.72%]. Because you have such high hit, have you ever played, or considered playing, fire? I think your gear suits it a lot better and I think you'd perform better playing as fire (obviously I'm looking at TTW/FB 18.53.0 here). What would you think of that? Oh, and if you are intent on playing Arcane, I would prefer you to drop your points in slow and prismatic cloak for at least 2/3 SoM (you could go ahead and take a point out of MA if you're comfortable losing the 3yd range, but that choice really is playstyle - I'd still like to see you pick up at least 2/3 SoM) because... well, slow is almost useless and prismatic cloak is a bit too PvPish of a talent to merit losing [553*0.08=44.24(*0.55=)] 24.332 crit (subject to increase with gear) over :]
Anyway, I'm blabbering on too much. I see good potential here, and I am willing to offer you a trial spot depending on how you respond to this #