A lot of things has been to test yet. At the present day, their published builds players can say that is one of the more interesting

It probably depends a bit on your type of play. Personally, I think having a high magicka pool and regen rate is a great asset. I play a tank or healer, and having access to magicka is essential for me.

For tanking you'll need stamina. Though, if you want to do a magicka based Templar tank, Blazing Shield is going to be your bread and butter, which you'd want to be able to cast without any resource issues. With that in mind, Imperials have a passive increase to max health, which Blazing Shield scales off of, so that would be a good alternative. Plus, Imperials have a passive increase to stamina as well, so for tanking they are a great option. I've often thought about redoing my entire character as an Imperial, but that's a lot of work and needs more testing for my playstyle.

For healing, I really just want access to infinite magicka, so the passives for High Elf are great.

DPS hasn't been a strong area for Templars, but in 1.6 that's changing a little. Several skills, like Biting Jabs, now scale off of stamina and do much more damage than before. And any skills that have stamina morphs have alternate morphs that continue to scale off magicka, while still dealing same/similar damage (depends on your stats). Templars also have a finisher now, Radiant Destruction, which deals a lot of damage, increasing on low health. Plus Backlash is an instant cast now. All great for increasing DPS, and magicka based.

So in summary, it depends. I have always played a magicka based character, so I choose the class that gives more of it, High Elf being one of the best ones. I've heard stamina based Templars do INSANE amounts of damage in 1.6, though, so if you really want to be a Templar but do damage that might be worth considering. Since your question is about whether High Elf is right for magicka or not, though, I'd say that yes it is. At least in the AD faction.

That's my 2 cents.