Yay Hidden Type :)
(I'll pretend I haven't played 10 games at most and will try to respond

)
I'm not going to address Dragonite at all, as I've never used it, nor do I remember encountering it too often.
Glad that Kyurem-Black was banned, to be honest.
About Heatran, I've used Grassium-Z extensively, even with Bulu support, and it was sort of underperforming. That may, however, depend on my own ability more than its actual prowess. I do agree that his coverage with Grass becomes more than decent (like ITH said, it takes opposing Heatran to wall it), and that his utility (Taunt, Magma Storm, Rocks...) is exceptional. I wouldn't ban it as it is, but it may be warranted if it gets too centralizing.
Concerning Shedinja, I've loved building around it! Honestly, Steel Shedinja did blow my mind as a concept initially. The advantages this typing provides have been perfectly described by our Tier Leader, so I won't go into them. As far as the element of surprise is involved, it definitely plays a role with Shedinja, especially for builders who like to shift from the norm. However, this is also the case for every other Pokemon in this metagame (albeit to a possibly lesser extent).
In my opinion, Hidden Type Shedinja is undoubtedly superior to his regular counterpart, with several typings adding great benefits (even Flying, to avoid Spikes, and Poison, to absorb Toxic Spikes).
Nonetheless, I really
don't find it ban-worthy.
This because, while it does warrant initial scouting to understand which is its Hidden Type (again, this is often needed for other threats as well), it can hardly ever capitalize on gained momentum. The fact that it can't cover all of his weaknesses at once means that 1 successful scouting turn is generally sufficient to determine the (viable) Hidden Type. To avoid scouting (and potentially losing Focus Sash), the Shedinja player is encouraged to switch out, a
very dangerous affair for Shedinja (whatever its typing, Stealth Rock is deadly). Deciding to stay in can be just as detrimental: Even at +2, its damage output is really underwhelming. Sure, it can cripple physical attackers with Will-O-Wisp, but this is usually predictable.
In my brief experience, it can switch in on several attacks (as long as hazards aren't a factor) and very easily generate momentum, but it has several factors hindering him:
Hazards (Especially Rocks, as I mentioned, but Spikes are often just as deadly). My teams had serious hazard removal game (at least 2 defoggers or 1 defog 1 spinner), and I still managed to lose more often than not, as soon as one of the defoggers got pressured enough;
Mold Breaker (one viable user was banned, but Mega Gyarados remains);
Rocky Helmet/Iron Barbs: A theoretical issue, which I luckily never encountered. Still, easy counter-game that would be far more popular, if Shedinja were more centralizing;
Pursuit: Unless Dark, Shedinja must rely on double switching more than it appreciates, if a Pursuit user is seen at Team Preview.
Predictability: Lack of any coverage because of its horrible move-pool means that Shedinja usually relies on its regular move-set. The best variation would be Sucker Punch on Dark Shedinja, but this would automatically hint to the Hidden Type.
Passivity: Even after having set up, its damage output is measly against any non-hyper-offensive threat. It does perform best against HO, spreading burns and revenge killing weakened, frail threats. Against most other MUs, however, it does the former at best, and is deadweight at worst.
Burns:
Unless Fire Shedinja, it really hates this condition because its damage output is severely reduced by the halved attack. Also, you're dead...;
Snow: No-one uses it, but it's still more used than Ice Shedinja

;
Honestly, I really did enjoy the few games where Shedinja seemed unbeatable (taking +2 Stone Edge from Lando felt great), but once my opponents understood what was going on, they started carrying at least 1 countermeasure, and it was the end of my winning days. In my experience, while it is undoubtedly better than regular Shedinja, it is hardly ever the defensive wincon it aspires to be, and I find it sufficiently balanced to be kept in the meta.