The one thing that would utterly make this game for me would be a horde mode where you and up to 5 friends stand your ground against an onslaught of increasingly difficult enemies. Each wave gets harder or adds more enemies, starting with dregs and goblins, adding in a few captains, then wizards, then ultra knights, ogres, strike bosses. Add RNG burn choices to different waves to keep mixing it up. Every 5 waves increases your loot worth upon dying and the rounds keep going until everyone wipes, so clear 5 waves and everyone gets a blue engram, clear 30 everyone gets an exotic engram. Defend the warsat does this to an extent, but it's nowhere near long enough and having a dedicated mode for it would be awesome.
That sort of happens now when you get a message that the enemy is invading (or something similar). I have had it happen to me in the rocketyard and the other area past where you first meet the hive (I can't remember the name). Enemies constantly spawn and get harder and harder until you are facing shielded yellow bar shielded knights, yellow bar wizards and reaver captains. If there are multiple high level characters in the area (thus the game adapts the spawns accordingly) it can get mental.
They need to take this and adapt it into a new public event (perhaps only triggered if there are enough guardians in the area). As you say adapt the RNG rewards to be based on how many waves you survive.
I finally got to level 29 on my main Warlock. That was a bit of a grind as I traded in the last of my Helium for marks, to buy armour, to break for shards.... Yeah you guessed it, I needed helium to upgrade my armour along with shards... URGH!
On my helium farming run I took down the fallen walker solo but **** that was tough. I don't know if this is normal but he happened to be flanked by solar shielded shanks, yellow bar Vandals and a Captain...

I was so focused on not dying to the walker, I died twice to the shanks.
Also played quite a bit with a friend to get our secondary (my third) characters up to level 20. My third Warlock character now switches between level 24 and level 29 depending on which Warlock has the armour. I Solo'd the Weekly heroic on my "new" 29 Warlock which was refreshingly easy (compared to running it in a 3 man fireteam). I got cocky at the end though and died right when the boss had a couple of shots left... It's funny running a level 29 Warlock which only has half the character abilites unlocked - no self revive here! Luckily my friend dropped in at the end (for the third run - the second time I rocketed myself in the face...

) to provide an assist.
Depending on the Strike, I will be running the Weekly Heroic and Nightfall on all characters. Feel free to join me if my fireteam is not already maxed. My level 27 hunter may struggle a bit (I prefer my Warlock(s) for Strikes) hence my next main objective is building shards for her armour.
I will also be running the daily heroics on all there characters so again feel free to join me if there is space. I need dem shardzzzzz

