INT and PIE has almost no effect so putting points in them is a waste.
The benefits of Int are marginal at the moment, but saying that Pie is a "waste" is completely inaccurate.
Increasing Int raises Spirit Dart/Phantom Dart damage by 0.25% - 0.58% per one point of Int. Sure this is not as big a deal as it used to be now that Dart has a long recast, but the Devs recently mentioned they are considering lowering it (see testing/data here
Increasing Pie increases the damage of DoT spells (Poison, Bio, Dia, etc), which definitely improve the speed at which you can take down NMs/Ogre/Batraal. According to Kaeko, DoTs are generally seen as the most reliable damage source for mages since they ignore dLvl, have low recast timers, and have great MP efficiency (see testing/data here
Pie also directly affects the amount of MP recovered from Siphon MP. This is especially important now that the MP costs of Cures/Raises has been increased.
It's a shame that the actual data/testing gets drowned out by all the misinformation...