True. it's basically a skill check (This is a Hard lock, open it with magic to rank up means you need to have a high enough Alteration to open it) but it seems realistic.
It wouldn't even be that hard to come up with some cool ideas. Its always jarring when npc's bring up numbers. If it were up to me, things like atributes and skills would all be under the hood...but that's just me. The guild master shouldn't say, "You're been the most active member I've ever seen in the guilds. Its obvious you love your work, and you do it very well. But you see, your destruction skill is only a 20. Get that to a 35 and we'll talk."
They should say, "You're been the most active member I've ever seen in the guilds. Its obvious you love your work, and you do it very well. I think I'll give you the test to see if you're ready to rank up. If you think you're ready, go ask for a D rank dual in the training room. Bruno will set you up with another mage, and you'll both dual."
And then in the dual, if you win or at least use a spell that requires your destruction to be over 35, you'd advance. It sure would be a whole lot more fun than a skill check.