I finally completed the Mage Tower for my Holy Paladin, buoyed mostly by the capped Artifact Power.
Actually, having the Mage Tower be active full-time was probably the biggest benefit. Previously, whenever I thought about doing the Mage Tower, it was never up. And when it was up, I didn't feel like doing it.
In any case, here's the Holy Paladin skin:
The healer challenge was pretty interesting. The hardest part was probably the section where you had to heal the ghosts, and it was challenging mostly because it didn't use the UI. So it felt like a completely new skill you had to learn.
The final section was rather annoying. The Ignite Soul mechanic, where your allies take damage equal to your health when the debuff expires, is supremely nerve-wracking. Especially when I realized--in the middle of the fight--that I was wearing [Highfather's Machination], which heals you when you drop below 50%:
"Alright, I'm standing in the bad, my health is dropping. I'm not healing myself. I'm down to 30%, good. Debuff expires in 3, 2, ... Wait,why did my health just jump back over 50%? OMG, everyone's dying! Heal, heal, heal!"
Ah well, it was a fun experience.
I also did the Retribution Paladin Mage Tower, fighting Sigryn's council. I think this challenge must have been very sensitive to gear level, and got significantly easier with better gear. With the level of gear I had, it was fairly straightforward once you understood the mechanics. Here's the Ret Paladin skin:
I also tried the tank challenge. It looks fairly doable. My problem is that everything is going fine, and then I get punted off the edge. That happened a couple of times, and I gave up for the night.
I think the Mage Tower Challenges were an excellent part of Legion, and I have mad respect for those people who completed them when they first came out. I also like the way Blizzard let increasing iLevel decrease the difficulty while still preserving a lot of the challenge. You still have to do mechanics correctly, even if you have more room for error. The Dev team did an outstanding job here.