No, I mean, for goodness' sake, we are talking about the maximum, the theoretical maximum. I didn't tell you it was a true-class, but sometimes it can be used if one bad skill was pushed in.

I'm telling you seriously—comparing the number of times the merchant is used in WT with logisticians in SoD is simply laughable. Moreover, in WT there is a lot of tension regarding the number of slots for secondary skills—fire and water are mandatory for full control. So the merchant will definitely screw up the hero's build.
P.S.—I consider my calculations regarding 4300 MP to be more correct than yours—we are talking about the amount of MP a hero has at the start of the turn, while what they gain during the turn is a different question—in SoD, for instance, you can use DD 4 times; 2 extra DDs also add a decent amount of MP =)