Roots does twice the damage of most AoE immobilises, dealing 18 damage at level 50 per target, so you're off to a good start.
Each Damage SO would add 6 damage per target to the power.
The procs have a 20% chance of doing 71 damage, or 14 on average, so they'll give you more bang for your buck. Slot some accuracy and you'll be good. A Kin superteam shouldnt need recharge or end reduction slotting.
Plus with 4 Kins you're going to be at the damage cap anyway once you all get Fulcrum Shift.
The proc damage won't be affected by +Damage buffs, by the way.
So yeah, sounds like your plan should work very well.
Carrion Creepers at level 26 will up your AoE damage considerably, by the way, and with all the Speed Boost you'll have it availabel at all times.
Do the procs check on every tick of damage, or are they limited to "once every 10 seconds?"
119088 - Outcasts Overcharged. Heroic.
Once per cast of the power. So on a base 8 second recharge, this can only be better than once per 10 seconds if you spam the power.
I did the same with Gravity Control and Ice Control way back when I9 started. Both AoE immobilises could take 3 damage procs, and this amounted to decnt (buit not great) AoE damage.
The main problem was End, at 15 end per cast these are rather draining to spam. Thats when it helps being on a Kinetics superteam, I guess 
I used Roots as my main damage dealing power from level 4 to level 26 on my Plant/TA controller, and it worked quite well.
Too many alts to list.
Thanks for all the responses. They confirmed what I was thinking, and it is great to know others were successful with it.
The nice thing about the nice damage burst with all the procs is that I can lead with seeds of confusion, then quickly do a fair amount of damage with roots so that I get the bulk of the xp when they kill each other.
And throwing 4 sets of seeds at once is great overkill, we almost always get every single target in a spawn confused, bosses included.
We've got enough SB that we can have seeds up every spawn, so we move pretty fast.
Some friends and are leveling up 4 plant/kin trollers that run together. We are currently level 23-25 ish.
I noticed that the Plant AoE immob has a fairly quick recharge. I think 8 sec unenhanced.
I already have it slotted with 2 damage procs (the immob proc, and the targeted AoE proc) and I picked up a third proc today (a lvl 31 PvP recipe proc - Javelin something I think?)
Can this AoE immob generate decent damage when spammed repeatedly by a kin user? Are procs the right way to go? Should I be doing something else entirely?
Any advice would be appreciated.