Ult is fine. It should absolutely not penetrate shields. If it did it would instantly become one of the, if not THE, most op ults in the game.
The issue with soldier is the lack of spike damage without a compensating mobility ability. If devs were to make helix rocket jumps allow soldier to get to much higher places (like ground to to catwalk on 2nd point kings row, for example), he would instantly become more useful in high ranks.