vampire on a templar is not a great idea. The reason being that a healer needs to be standing as long as possible. Vampire itself is a glasscanon type of build.

You did the good thing by going destro/resto full magica. I do think you might want to pump the magica further up and let the health drop behind (no need to respec, just put everything in magica from now on).

What armor are you using?? I personally think the gain of armorrating from heavy armor is worth more then the gain of magica from light armor. To explain this.

With heavy armor, you have better protection to loosing health. This means you can choose to have more magica then health in attributes, food and mundus effects. Cause, when self-healing, your magica decides how much hp you restore, but you total amount of hp decides how much healing you need to be full it is more productive to prevent loosing healthpoints compared to stacking more healthpoints that require healing.

The biggest issue however is that with a destro/resto setup on templar, you picked a setup that is very good for groupplay, but less for solo play. The reason is that templar doesn't have a pet like the sorcerer to tank for you. So you need something to keep your foes (mostly) at more then an arms lenght. This can be done with kiting them around, dodging and rolling, but also with knock backs like piercing jeveling. With the amount of magica you got you should be able to spam it regularly, the knockbacks help a lot in creating the distance between you and your foes and last of all it is decent damage.

The fire damage vampires take is going to be reduced significantly in a coming update, so vampire builds will be become more viable across the board. I have a Templar Healer myself, and the only reasons I've decided against going vampire on that character are 1.) my character is a dark-scaled, striped argonian with skull face painting, a look I've become attached to and really like, and I'm not sold on becoming an ghostly albino lizard overnight and 2.) I'm a Healer, and currently the fire damage would just make it extremely difficult to effectively fulfill this important role. However, if you're looking to up your DPS output, vampire might still be a good addition to your build.

Unfortunately, magicka Templars don't have a lot of options when it comes to DPSing. Sure, there's a few Destro skills, Puncturing Sweep, and Radiant Oppression. And that's about it. Stamina Templars have cornered the DPS market for sure. I run Resto Staff as my main, but I actually end up using my 2hander more often because I solo most of the time. I don't have any points invested in stamina, but 2h still hits like a truck. Plus, it (oddly enough) increases my spell power. I might switch to Destro later.

Out of my six characters, I'd say my Templar Healer is actually the strongest with the most survivability and so far has been the easiest to level up. I disagree with the suggestion to incorporate more heavy armor; if you're a magicka build, mostly light armor is the way to go, period. You need those magicka passives. You're not a Tank, so stacking HP shouldn't be your priority. The extra health might help when self-healing, but I wouldn't sacrifice that precious magicka for it.

I've encountered one decent-looking magicka Templar DPS build; I'll post the link below so you can check it out as a potential set-up for when you're not healing.

http://tamrielfoundry.com/topic/aedrics-warrior-magicka-build-templar-dd/

You should focus on either magicka or stamina but you should still use both power pools. If you're wanting a Templar DPS/Healer then I'd recommend going magicka DPS so you don't have to swap gear since healer should always be magicka, then even in DPS mode you can switch to your resto staff to do heavy attacks to regain magicka.

But being magicka based doesn't mean you have to use a destro staff, your weapon damage determines your weapon power AND SPELL POWER -- so as strange as it sounds, 2h and dual wield you actually have more spell power than using any ranged weapon.

You could make a DPS/healer without using any weapon abilities if you wanted. Blazing spears, Dark Flare, and Radiant Oppression (great execute ability) all buffed with Entropy is a viable bar for magicka DPS.