1. Analyze the stats of the card (HP, Weakness, Resistance, Retreat cost).
60hp for a pokemon that doesn't evolve isn't good. Darkness weakness is ok, the only card I can think of just now that benefits from this is Umbreon UD which can now OHKO it but there's probably others in the next format. Resistance to colourless is nice, but won't stop a Dragon Rush. One retreat cost is decent, especially since few pokemon next format have no retreat cost. Being Lightning Type gives it type advantage over cards like Gyarados and Yanmega Prime but it's attack lets it down.
2. Analyze the attacks (and/or Poke-Powers, Poke-Bodies) of the card.
It's attack, for one lightning energy, does 20 damage for each energy on the defending pokemon. This attack isn't that great just now, for example, the two decks I mentioned above will most likely try to attack for no energy so you can't even damage them. SP pokemon use very little energy (most will have one or two energy on them), and the most popular pokemon that attack using 3 or more energy now can easily defeat Rotom.
If this card has any use, it's "Mischivous Trick" which swaps the top card of your deck with one of your prizes. If you can find out what your prizes are, this is good, as you can pick up any card at any time from your prizes in exchange for the top card of your deck. But I think the problems outweigh the benefits. First, it can be sprayed, and if you urgently need one of the cards in the prizes, that could be decisive. Second, unless you also know the top card of your deck, it's a big gamble as you might be prizing a better card, without knowing it. Third, unless you have a way to get cards later that turn, it could be another turn before you actually get the card. If you'r opponent uses Judge, you could lose that card in your deck and use more resources trying to get it back again.
3. What combos can you use it with? How so?
A card that lets you see your prizes such as Alph Lithograph 4 or Azelf would help it, and any card that allows you to rearrange the top of your deck (Slowking HGSS, Research Record, Pokedex) so you know what you're getting rid of.
4. What techs can you use to combat the weak points?
I don't think anything would help it significantly, Unown Q can give it free retreat but that's all I can think of.
5. How's the artwork?
It's OK
6. Give it a rating, and explain why you have given it that rating. You can also rate the card by rating the thread itself (out of 5 stars).
In this format, 1.5/5. Azelf is a more superior card and it's attack won't leave a dent in this format. However, it might have some place in a HGSS format. With Azelf gone, this is the only card that can let you take cards from your prizes, and it could counter decks that rely on getting out lots of energy on your pokemon (such as Roserade UL, Tangrowth COL) if they become popular. It won't be as popular as Azelf though, since it's slower and less reliable.