You're in a doldrum of the leveling system, unfortunately. One Tamriel works by handing low level characters a ton of handicaps to their stats, including gear. It's howmthey can kill c160 monsters (which is what everything is set to). These are reduced as you level because you're supposed to replace the power lost on your own. So I see loooooots of posts from c160-300 players saying what you're saying.

Some tips:

You're correct to dump all attributes into magic and to adjust health needs via armor enchants. An attribute is worth 115 stam/magic...one piece of armor is ~900. It's easier to use armor enchants to fine tune.

It goes without saying...but needs to be said...that you should spend points in EVERY helpful passive. If it gives you a buff, even tiny, go get shards and spend the point. All class passives...all in weapons you use...all in light armor, and some in heavy if you wear heavy. And any others in the tree that help.

My Templar healer felt horribly squishy until I learned to slot and spam Harness Magicka under certain circumstances. If you've overlooked this skill, it's fantastic on my Templar in vet combat.

At your level, it's now about improving your gear type and quality. You should be working toward an appropriate set configuration: 5/5/2 or 5/5/1 or 5/4/2 or whatever maximizes each gear slot. (Alcasthq.com has great builds...and he always cites secondary "starter armor" that's easier to get).

Until you have more CPs (which will help you be way tankier), there's no shame in using 1-2 pieces heavy armor.

Quality is going to count more for you now...you probably need purple gear in addition to the right sets. And the gap between all purple and all gold is significant. You don't want to rush and spend gold mats on a set you might not keep long....but if you find a setup that really works for you, going gold piece by piece is helpful. If nothing else, get those weapons to gold - the damage boost is huge. For an initial gold mat investment, Julianos is a fanstatic set that would serve you well. It was the first magic set I made gold, and I still use it...and handed it across three vet characters.

Make sure your CPs are invested wisely. Some massively outperform others. Again, Alcast is a really knowledgeable player and his builds always have a 300 CP recommendation. This will point you in the right direction...although CPs will shift massively in June, so make sure to check thenguides then because you'll almost certainly need to recast.

Those are some basics. And perhaps there's something there you've overlooked, in which case I hope the tips help. But the bottom line is that it's not just you - CP160-300 can be a struggle. Make small improvements where you can and keep on earning those CPs. You'll get stronger over time.