I believe DPS mundo is viable, and yes more viable than Tank Mundo. A Hybrid actually works well.
Problem with your build though is its best to grab some attack speed at the begining to capitalize on the massive attack damage you gain from massicism, this will lead to early and mid game dominance. I would suggest something more like this:
For a Pure damage build:
For a Hybrid Build:
I would tend to lean towards more of the Hybrid build against most teams, probably depends what kinda of CC and AoE you'll be running into, and what kinda of CC you have on your team.
Note: Make sure your team is aware that you are in fact not really a tank... this should really be done anytime you're mundo.