For those who aren't familiar with the changes to the XP formula, I'll tell you the old formula, and then I'll tell you the NEW formula.
3 XP per Spell you cast
3 XP per Spell cast by your Minion
3 XP per 0, 1, and X Ranked Spell you cast
3 XP per Pip for 2-7 Ranked Spell you cast
0 XP per Spell cast by your Minion
What does this mean?
It means that while under the Old System, Conjurers and those who used their minions more often would gain more XP / battle than most others.
Under the New System, you get more XP as you progress (Storm Lord is 21 XP per Cast, even if fizzled).
Under the old Formula, I and my Sprite wracked up over 200 XP in the Sokkwi Keymaster battle (she was attacking and I was healing as my Attacks were hiding!). Under the new system, I'd be lucky if I get even 87 XP for the same long, drawn out battle.
Anyways, the Formula wasn't really broken, but they 'fixed it' anyways.... *sigh* my baby Myth needed the XP from the Minion... he would have gotten well over 100 XP in the Yakedo battle alone if the old System still worked... instead? He got 30 XP.