It's basically ME3 multiplayer on acid, with ninjas. I'm so fucking down for this.
Not to rain on your day or anything, but it's nothing like ME3 MP.
ME3 MP felt like a 4 man stand-off, that required constant communication and co-ordination.
Warframe requires almost 0 co-ordination, even at the "hardest" difficulty.
Difficulty is absolutley artifical, it's merely a gear check and HP bloat.
Gameplay consists of wave after wave of poor AI that need little more tactics than "run and gun" to deal with.
The game is literally just an endless gear treadmill.
The only real similaties are:
It's co-op.
It's sci-fi.
Gear progression is horribly RNG based.
At first, the game seems awesome, but soon you'll realise that all it consists of are repetitive missions that you grind over and over to level gear.
"End Game" is either endless defense (requires no tactics aside from: stand in defense bubble, spam powers and weapons), or endless survival in which you kill stronger and stronger enemies over and over.
To get new frames you need to ginrd bosses over and over and hope the parts drop. Sometimes they drop nothing, so there's not even a guarantee of a drop every time. Some players have reported grinding for weeks without getting all parts.
Mods are also tied to rng drops, and are required to boost yoru frame and customise it. I've played for 400 hours and have yet to find a single Tactical Pump mod (not game breaking, but it is a very basic mod and highlights the issue of RNG being tied to progression).
They often add events, and new content has brought new ways to acquire certain frames (ie: Nekros acquisiton is a big improvement), but it's still RNG based and it's still only a gear treadmill.
It's a shame, the foundation is very solid, but the devs don't seem interested in developing it further. Right now, all they do is release new gear to grind for and level, and new areas to grind through, there's been no enhancement to the core gameplay for a while, and now it's being offcially released for ps4 I doubt it will ever happen.