I play teemo as a main, I play mostly mid in the games i play, but wing it quite a bit also. When soloing mid, as i'm harassing my counterpart with blind dart and my poison, i'm always keeping an eye on their lvl so that i know exactly when it's time to play conservatively and stay close to tower, that time being, when they get their ult.
Yes, when playing teemo I am always weary of my fellow laners ult, whether it be ashe, fiddle, annie, tristana, cho, yi or anyone really. Then it struck me as someone used an/a oracle/ward for the umpteenth time to avoid/shoot down every single shroom i placed after they fell victim to the shroom trap that caused that 1st death to my hands.
I realised that my ult is a load of ****.
It's easily countered by 400/150 gold, it's effectiveness is lowered by cheap boots, it takes a long time to set up an area so that the shrooms are effective as anti-gank/pro-gank wards, the damage doesn't stack so someone can run thru 4 of my shrooms to get to me and shake it off as they give me the final blow and all in all, my ult just doesn't worry anyone. It's mostly a nuisance to other players, "oops, tripped a teemo trap in the grass, i'll just pretend to walk away so in 2 secs he won't know if i'm back in the grass or not.... dmg? what dmg? my hp regen took care of that already"
Sure I love it when I'm laning, it's saved my bum quite alot, and get me a kill/assist every now and again (rarely) but it lacks the effect of an ult. I'd be more satisfied if they removed camouflage , put move quick as the passive, made the shroom the new W and gave teemo an ult that really made ppl go "oh crud, the teemo's lvl 6, I should care a little from now on"
Cause let's face it, mid to late game, the most shrooms do is maybe help your team get away from a bad gank if you had enough time to set down one for a getaway.
TL;DR
Teemo's ult sucks as a ult.
Too easily countered with ward/oracle.
Take's a long time to set up and isn't rewarding when someone runs through every single shroom you placed.
Only usefull early game when your laning, takes too much time to set up mid/late game to be useful.
Only a nuisance to opposing team members late game.
And yes I know I could go AP build to make the damage more threatening but if you were reading properly, you'd realize that it doesn't matter when ppl buy oracles and wards to counter the shrooms.