I was doing 1v1 and a level 28 killed me with 1 hit!
-Jordan Jadecaster Magus Diviner level 32
Ok, wow, not much here. You didn't tell us schools, spell used, reason you think it is overpowered, what strategy you used that rendered the attack possible, etc. I would guess it was either Storm or Balance, right? Try changing tactics and going for defense over first few rounds. Then while the enemy is clearing shields, break through their defenses and attack.
May I ask how did he kill you? Because there could be a few flaws in your strategy causing that.
Since you are storm, you very easily are gonna go down in one shot if you don't shield. You also have the option of using Treasure cards to ensure you get what you need when you need it. Now if this is Ranked PvP, you may want to put it off a bit since a lot of adepts and maguses have strategies that are hard to counter unless you use a similar strategy.
Now, if i were you, I would gain a level so that i could pick up darkwind, since it's fairly useful against those other adepts and maguses you face. I also would considering training Tower shield and weakness, as those are nice to use in PvP as well. From there, you could practice your strategy to solidify it's usefulness, THEN return to Ranked to go for warlord again.
There was a lot left out of your post, but the card you MIGHT have encountered could've been the Tamauji Treasure Card, from the Kirin's hoard pack. In a previous post by whose name I've forgotten, he states that the treasure card will hit again and again and again. When i tried it out, it hits four or five times for 6 pips with damage intervals at +15 from the base of 625 (I think), scoring around 24k-30k of damage altogether, assuming the defender has no resist to ice and the attacker has no ice attack boost. Now this is an example of an overpowered spell, which, thankfully is being fixed tonight.
Sounds like you either went in with low health or they used a treasure card on you... or your strategy needs improvement. They could've used a bunch of shields on you and themselves to improve the spell, and then just use a very powerful spell. It's possible.