What about tweaking 
shrooms so that when you walk over more than one the remaining damage from the first is dealt instantly? Kind of like 
double bombs. It's pretty painful watching tanky champs, or champs with shields/heals just walk over your minefield taking minimal damage. Thoughts?
Would likely make stacking multiple shrooms too effective. Bush edge? Better drop in 10 shrooms. Enemy steps on them.100-0 and dies almost instantly. Not healthy gameplay. And this is coming from someone who loves playing .
he doesn't need a buff for his shrooms they are already extremely useful for a multitude of reasons. tons of damage, slow, free ward.
if you place them badly you don't deserve the full damage on both to hit your enemy.
I would love to see some sort of mechanic wherein if you are under the effects of a shroom and step on another one it either does a small(not full damage) extra burst of flat damage/increased percent dot or something. Nothing too major, but something to dissaude a tank from walking over ALL your mushrooms.
Honestly, I think a better way to buff the shroom is to enhance Teemo's E damage to enemies under the poison effects of the shroom. Maybe add a 20% bonus to the DOT from his E while they are poisoned by the shroom as well.
Unfortunately that just results in Teemos piling shrooms on one spot, then spending all their effort luring a victim to their deaths. He'd be much less useful for map control if he concentrated too heavily on huge damage.
