To elaborate:
Pandora is good, but you have to play with the mentality that your general should be high (>12) on health by 7/8 mana (whenever you summon it) which can be difficult to do in a meta with so much burn and so little heal. Pandora wins the game too slowly for it to be useful otherwise. On the plus side, Pandora is more likely to not be removed completely due to its 2 body minimum, which helps a lot in sustaining your health advantage.
Synja is better for tempo, imo, because it provides a much more immediate threat (7 attack) while helping you gain tempo/board control via its ability, one of my favorites in the game. It can close out a game very quickly if unanswered.
Dark Nemesis provides not a lot of immediate threat and only one body, however it promises face damage if unanswered, and ramps up in strength very quickly. This makes it valuable to decks that are more burn-centric, particularly those that run out of cards. A Nemesis dropped out of reach has won me quite a few games just by dealing 4 face damage when it looked like I had no hope to burn the last little bit of my opponent’s health.
Still around if much less popular than it used to be is Archon Spellbinder. It can temporarily shut out decks that rely on comboing/expensive spells, and at minimum often gets you mana tempo. Its statline makes it fairly dangerous. However, it’s not consistent value, making it more of a tech card.
As far as ‘lump of stats cards’ are concerned, my favorite is Brightmoss Golem. I prefer it to Stormmetal or Dragonbone or Astral if you need a threat due to its high health and cheap (relative) cost. Dragonbone is good, but if your opponent answers it it gives you nothing and loses you tempo- Brightmoss requires about as much removal, comes out at lower mana which makes it easier not to lose much tempo, and will still deal similar damage by 8 mana, or if buffed.
Grailmaster, Khymera, Mechaz0r, are all cards you actually build your deck around a bit, so they’re in a different category from the aforementioned imo, and also good wincons.