Hi there, I had some thoughts on some specific cards in the HP TCG. Here they are:
This card is most helpful if you fill your deck with creatures that have high health levels. Examples of creatures like this are Unicorn, Guard Dog, or Kelpie. When these creatures have damage on them, you can simply slap down this card, and they're completely healed. If you stick four of these in your deck, and end up with a couple in your hand, you can slap a lot of damage on your opponent before he or she can do anything about it.
Draco's Trick
I can't see why a person wouldn't put a couple of these in their deck. Just look at the reward for the adventure Diagon Alley (draw any number of cards) or Meet the Centaurs. The reward for the latter is, "You play with your hand up for the rest of the game", so that would mean your opponent plays his or her cards up for the rest of the game! Obviously, the number of ways this can be helpful are endless.
Hagrid and the Stranger, Mysterious Egg, Ollivanders
If you're creating a deck with a very specific strategy, these and cards like it can help ensure that you get the cards you need in your hand when you need them. If you have a strategy-specific deck, don't let it get caught without these!
Till next time,
The Sybillium