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Best at rush is a tough question, Forcemasters, Adramelech warlocks and Straywood beastmasters are the best rushers of their types. Forcemaster to rush in melee, Adramelech warlock to rush with attack spells, and Straywood beastmasters to rush with creatures. There is a strategy known as "Johktari Rushmaster" to utilize the Johktari beastmaster's fast trait in order to make an attack spell rush with it, putting hawkeye and akiro's favor on turn 1 and then double hurl boulder on turn 2. I never tried it, but It is a well known strategy (Arcane duels have a video about it, and if I am not mistaken, They invented this strategy).
Best economy is the necromancer. I've never seen a game involving a necromancer that lasted more than 12 rounds with his opponent victorious (except for a dual between two Necromancers).
About buffing oneself, assuming you mean a mage that kill it's opponent with melee attacks it buff by bringing a good weapon + bear strength + vampirism + defensive things to make sure you are not dead before you kill the enemy mage, I think the best so far is the forcemaster (though Paladin could be better, I don't have Paladin VS Siren yet). Many mages combine buffing themselves with other things (such as bringing creatures), which makes priests and araxian crown warlocks good at such combined strategies as well.
