Nah, I don't think he's top tier at all, but he is a really decent character.
Firstly, when you talk about how good/bad a character is you really need to compare them to the rest of the viable cast.
Does he pressure and/or chip better that Dash/Fireball Cancel characters like Scorpion, D'Vorah, etc.
Does he have mixup/vortex potential similar to Raiden or Erron?
Does he have High/Low hard-to-blockables like Quan Chi or Cassie?
Does he have high meterless damage potential like Kung Lao or Mileena?
Safe wakeup like Goro?
Some of the characters I mentioned aren't even top tier and he has way less than that.
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However, I do think he's a decent character, because he actually controls space. Not in a broken projectile spam based way either.
I was naive and biased before but after his MB on Block 'fix' (not buff), I started to realise that the character is actually quite well thought out.
You're essentially managing the space between himself and where his Hell Sparks end. He's a proper zoner. EVERY variation that he has allows you to harm players that want to be outside of that range. This can be done by reacting with teleports, ground pounds or flicks/fireballs. So he kinda operates like Sinestro/Shang.
Choosing variations actually changed people's perception of the character itself because I reckon he's meant to played quite similarly in all variation. We all wanna run mixups all day, zone all days or counter poke all day but he's probably meant to be more patient than that.
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I do think he needs some changes, though.
-Give Amulet Curse armor but make it -5.
Hell Sparks can now be meter burned on block, so Amulet Curse is actually not that useful because Hell Sparks are hit-confirmable, delay-able, have 10 extra frames of advantage and leads into combos.
Just make it a safe reversal move that costs bar, considering it does the same damage as the regular version (9%).
-Summoned Fiend/Summoned Slam to have much better tracking. So it's more reliable to combo with and catch people running. This was suggested by REO here:
http://testyourmight.com/threads/my-predictions-for-the-next-balance-patch-post-yours.52410/
-Hell Blast to have reverse trajectory.
This is currently the move that has the most wasted potential. Yes, it does more damage and is fast but you still need to Meter Burn to make it safe or combo from it.
I hope NRS will consider making the move start where the regular Hell Sparks end and travel back towards you. This should be accompanied by the frame data and damage being adjusted to match the regular version.
Why is this significant? Regardless of Shinnok's full screen options within his variations.
He best attribute is managing the space that Hell Sparks covers and working around it. If he could pay a bar to drag you back into that 'zone' (zoning character, see?) then it's up to you to to spend further bars to make those situation safe or advantageous.
Also, we all know that Shinnok's damage is currently an issue. Understandably, Mimicry's damage boost is NRS reasoning. Fair Enough. Well, if Shinnok players want to choose the lower damage option they can have weak unbreakable projectile combos.
Anyway, that was my thoughts on the character and 3 changes that I have spent a long time pondering on.