It was semi-nerfed a few years ago. Prior to the semi-nerf patch, when discorded the game registered your real skill level as the discorded skill level so your gains would reflect having the lower skill level. Effectively making your gains come much more often. The semi-nerf changed the game to take into considering your REAL skill level even when discorded so the gains became slower.
You will still gain skills faster however because with any casting skill, your gains are based on how often you can cast spells. Being discorded lowers your skill level letting you cast lower level spells which use less mana. Using less mana to cast lower level spells enables you to cast more spells over time thus increasing your skills gains in an allotted time period over not being discorded.
The Satyr trick isn't as effective as it once used to be but it still beats not using it at all
Put a -29 mage weapon in your hand while discorded makes it work even faster for magery
(It was in the patch notes a few years back but when and where I couldn't say)