Well, I'm not a long-time player (actually only found this game 2 days ago), so I don't have extensive experience, but I've tried a couple of different mono decks (different elements), some mixed decks (mostly the ones suggested in the wiki), and found the vampire darkness deck absolutely the best for grinding lvl 3 (and also quite successful in occasional PvP).
Since I really started playing a bit more intensively yesterday, it only took me one day to have the following setup:
Mark of Darkness (of course)
12x Obsidian Pillar
1x Obsidian Tower (just upgraded today, so had 13x O.P. before)
4x Devourer
6x Minor Vampire
4x Black Dragon
4x Steal
4x Drain Life
1x Dusk Mantle
1x Eclipse (upgraded yesterday)
1x Vampire Dagger (got it from the 500 ranking quest, upgraded yesterday)
(38 cards in total)
My current stats with this set (I reset the account, so these stats are for this set only, not the other tests!):
Won: 138, Lost: 11 (a couple of those losses were in PvP, one was trying Top 50, and one was trying a Fake God, so I can say only about 5-6 losses are to lvl 3, and at least half of those were when I tried a modification of the mono darkness set — see below; i.e. I can say I lost to a lvl 3 using the vampire set perhaps twice or three times (!) out of more than a hundred games).
The set was inspired by the Wiki (Level 3 Mastery: Vampires (
http://elementsthegame.wikia.com/wiki/Level_3_Mastery:_Vampires)), but I modified it slightly.
Only yesternight I came across the forum, and started reading upon mono darkness decks. I read the thread, where it was stated that using dragons instead of vampires is better (
http://elementscommunity.org/forum/index.php/topic,70.0.html). So I decided to try it. I bought some more cards, and ended up with the proposed, improved version of the abovementioned set (in one of the later posts).
My results definitely proved (to me, of course...), that the vampire deck is way better. First of all, with the Vampire deck, I tend to get EM quite often. With the dragon deck, I never managed to get it (out of about 20 games). Second of all, the length of the game was comparable (number of rounds required), despite the fact dragons definitely hit harder. And third of all, I managed to lose 2-3 (at least) games with lvl 3 using this dragon deck. So I switched back.
Maybe there are possible improvements to this vampire deck (e.g. less Steal, more Devourer, hard to say), but the shape it's in now is very comfortable and requires little thinking (so it's good for grinding). Maybe it's a bit larger than usual, but still I find the probability of getting the right card is alright.
To sum it all up: I definitely say yes to a vampire deck.