The first thing you have to keep in mind is that in dungeongroups, it is almost always the healer that is a templar and as there is also a shortage on healers, people often expect the templar to heal.

that said, any class can fill in any role. There is nothing wrong with a nuker templar or a tank templar (with a few remarks)

I'll first handle my remarkts bout the templar tank.
In GW1 there was something as a wammo. This was a warrior-monk and it had a pretty bad name. Not because a wammo was bad to start with, but cause many where bad groups just stopped excepting them. The templar tank is simular to the wammo.
The simularity is that people expect them to be good at tanking cause they can heal themselfs (I've never played WoW, but I understand simular to the Paladin there). Besides that damage mitigation is much better to survive than outhealing the damage, there is another very important reason for this.
Most heal skills scale of magicka and most tanking skills (including blocking) scales from stamina. Now so what. do many think. But the effectiveness of stamina skills is based on the weapon damage. This is again based on the total amount of stamina. The magicka skills is effective based on spelldamage and this is based on the total amount of magicka.
So it is better to go for full stamina and stick to those to max out weapon damage. Or go full out on magicka and max out magic damage (also increases the heal per second). So templar tanks work ok, but only if you concentrate on stamina skills with as much stamina as possible.

Why giving this preech while you obviously figured out it is a bad idea (dunno if you did the above, but still).
Cause im getting to your original question.

Assuming you got all the skillpoints required (should be a breeze). You can have everything ready for a healing build AND a ranged caster dps (using destro staff). OR you can have everything ready for a tanking build AND a melee DPS-build.

As you don't want to tank, and as there are so lil amount of healers, my advice would be to go for the ranged dps caster. Just so you keep your versatility as an option.

Thank you for your input! You werent preaching!
I appreciate it tremendously, that you left such a deep reply for my question.
I had the feeling you cant really accomplish anything with a hybrid stamina/magicka tank, and you confirmed it.

I have around 30-35 skillpoints, and healing intrigues me, so i might try that if its viable with the amount of skillpoints i have.
Some tips on attributes & skills would be awesome

Templars can tank and do it well but they really shine in AOE tanking, grouping up 10-20 mobs walking backwards spamming puncturing sweep. I have a hybrid build its for PVE and PVP, it has excellent utility and survivability and support, however it lacks damage. First thing ill mention is as a Templar you have basically the worst resource management, so you as a tank may want to lean more towards regens then maxing out stats.

1h+shield

-pierce armour
-invasion
-puncturing sweep
-channeled focus
-Honour the dead(getting a huge boost next patch)
-Rememberance

1h+shield

-purifying ritual
-Razor caltrops
-Vampires Bane
-Radiant Opression
-retreating menouver(compulsory, Templars have no escapes)
-Any damage ultimate ice meteor, solar disturbace or soul assault.

im on 15k mana and 15k stamina, with my CP's in block cost reduction, mana+stamina regen and healing/spell crit. what results is a character that can endure almost everything thrown at him endlessly harass and disrupt the enemy(PVP) or in PVE it can easily group up 10+ equal of higher level enemies and jabs spam them to death without losing any HP, and can self heal through most bosses if required or if you have the patience solo bosses. 1.3k regen of both stam and mana or higher is basically what u want.

But remember its my support/tank/harass build it doesn't do that much damage.