No. The two are not congruous.
Machnisei Rachamim asks the angels to bring our tefillos before HKBH. The implication is that, without their help, our tefillos will either not be heard or otherwise have greater difficulty getting HKBH’s attention. This contradicts the idea that we do not believe that any intermediaries are necessary between us and HKBH. I can daven to Him and He will hear me – angels or other beings not required.
Asking someone to daven for you is different than the above. I’m not asking the person to convey my tefillos to HKBH; I’m asking him to add his voice to mine in prayer to HKBH. In this scenario, the other person is not an intermediary. His prayers don’t make sure that mine are heard — they are simply added to mine. As such, it’s not the same scenario at all.
The Wolf