I have not seen a 5* from the factory yet with over 700 tanks produced.... but I have got a lot of 4*'s so it's not terrible.

FYI Max Commander level is 50.... so once you hit that it's only tanks that will level and thus commander level based events will be easier.
Seems that the hardest time is commander lvl 35-50 where it's likely your commander will start to out level your tanks.

And as for the event maps... I can clear tile 1 and the first 2 missions of tile two with just the commander arty ability, the second 2 of tile 2 are easy but tile 3 missions cost me tanks almost every run. Tile 4 I might be able to clear but it would wipe out my team each time... and by wipe out i'm talking 10+ losses each time.