Is 5% discipline a make or break in an MP war? It was claimed that an 8% discipline advantage is OP (although without giving in-depth detail, that advantage is really 3% instead of 8%).
And PMR is very, very, very (, very) powerful.I haven't played MP but:
OP compared to what? The late-game NI gives 25% and Prussian Military Reforms gives 20% so it's not much compared to them.
Discipline is all about inflicting/taking casualties. Certainly it's an advantage but you can balance it with superior numbers (preferably combined with good WE modifiers to compensate for the WE from your increased casualties) or leaders.