Well it all depends on what job you want your engineer to do...
There are two types of engineer players, one which is the standerd support engineer and the other an offensive engineer.
Engineers and Comeng. LOL.
What ever your play style you'll always want 6 heal, 6 transferance, at least 1 on revive and only 1 on pain.
The rest I'll leave up to whether you decide what your strengths as an engineer are, as a supportive or a tanking offensive type.