Why do we have this class if we cant use it?

Well,when the game was opened they said that engineer class was in construction yet,but i think they were focusing in the other versions of the game(Taiwan,Hong Kong and etc...) but it's just a guess...

If they add it they should add other classes for other races but that's the problem, i think we have nothing to do with majin and nameks, they wouldn't just say that they gave up on the eningeer so they just left the way it is now.
That's my guess.

Maybe Engineer will launch only when they prepare for all races...

maybe the engineer will be a human buffer , maybe even with some weaker healing "powers"

i think he will be lable to repair the equips and to make than with buffs harder to brake.
i just can't imagine someone like bulma as a super sayan.

Maybe they wanna try combine androids with Engineer. To many possiblities to go with that class.

First we need new classes for all races...

That's exactely what I think.

Actually, I think humans should be the only race to have a third class. The way I see it is that Engineers will be more of a "support" kind of class when compared to Martial Artists and Spiritualists. Nameks and Majins both have classes that range from offense to defense, while humans only have offensive kinds of classes. Mech Maniac in particular I see being very similar to Poko Priests, while Gun Maniacs could have skills that buff themselves or others since, well, guns aren't really going to do much by themselves.

That's just my opinion though.