[Defense Mission Rewards To Scale With Wave]

Keep in mind this is meant to be a Co-op game. It's not just about farming and bettering yourself, but to have fun and interact with people and friends. Honestly, I only play Solo unless a friend is on, and it doesn't take away from the experience. However, this game, being strictly co-op, doesn't have as much of an incentive to keep on going. PvP games do, because having better equipment directly means you are better in the game, hence better than others. You don't get too much of that feeling in Warframe. Or maybe that's just because I play solo.

[Fights Between Factions Need Some Love]

Same thing happened to me, except it was an infested mission and a Grineer force landed. Kinda weird to see both factions in one game. I wonder if anybody has seen three. 

What they could do to make it more logical and interesting would be to have a relatively large, open map, akin to those used in Defense missions, and use multiple spawn points on sides of the map where the different factions would spawn. They'd be hostile to one another, and knowing the AI, probably wouldn't do very much. Your mission could be an Exterminate one- where you have to kill them all, which would be more difficult because there would be greater numbers of enemies at once, or a retrieve mission (artifact), where the orokin artifact or reactor would be between them.

Just some ideas.

[Update 7 - "stormbringer"]

Love the sentinel, great job!