Originally Posted by Geryth
Because Karma does everything Orianna can do but better, except work as a straight AP carry top.
Karma is just like Soraka in the bottom lane. She has Infinite sustain, can easily wipe minions, and can build tanky so that she is near impossible to play aggressive against to push her out, and she can herself against many champions play aggressive and push away. Orianna in the bottom lane is easily predicted. She's all about her ball's placement. Once she Q + W's a minion wave to wipe it, you know you have 4-5 seconds where's she's completely defenseless. Orianna also doesn't heal and is easy to play aggressive against, you can predict her ball's movements and easily come out positive on aggressive trades, as her shield is not as strong as Karma's.
Orianna in the top lane as a support is very sub-par. Her ratios AND bases are low, because all 4 of her abilities can deal damage. If she's supporting she's constantly throwing out shields and placing her ball for slows and speeds ups with her W. She's wide open for an assassin. As an AP Carry top lane, her ratio's keep her from doing as much damage or being as useful as other picks like Ryze, Cass, or Gragas. And also, she's extremely vulnerable to assassins, who are very popular on Dominion.
Orianna has an extremely high skill cap as well. She has to watch her position, her balls position, and everyone else's position AND predict movements ("Is my tank about to run in an initiate? Shield him and R when he gets inside them!") EVEN when you can make the stars align by playing with the best positioning you can with all of those factors, her ratio's make her support and damage very "meh", and with the best of skill she doesn't shine out like other champs that do similar roles. She's in a very odd AP Carry / Support spot, and that makes her dangerous to buff, but overall weak because of it, ESPECIALLY in sub-optimal hands. Karma shields, speeds up, and heals, and can build tanky while doing it well with good base values. Orianna HAS to build a lot of AP for either role, which makes her squishy and vulnerable.
As a heavy SR and Dominion player of both Karma and Orianna, I respectfully disagree.
You say "If she's supporting, if she's carrying" The thing is, much like Karma, she does both simultaneously. That's what makes her so difficult. Much like Karma, you build AP to carry and support.
What can I do to prove her viability?
And again, I understand she's very hard to use effectively. But that should not be cited as a reason to have her in tier 4.
The thing is, I'm not asking for the stars here. I don't think she is a T1 or T2 pick even in perfect hands.
I'm asking you to say "Sure, in the right team comp in capable, experienced hands she can be an asset to her team"
Tier 3 - These are champions that either take more skill to be successful with or work as good counter picks, but enemies generally have more options to deal with them.
This is your tier 3. She belongs there.