Actually, it depends on what kind of game you are making your hero for. If you are making him for hero vs hero, assasinate, stealth, switch weapon, and coerce (for summoned reinforcements) would be the best abilities.
If you are making your hero for ordinary maps, coerce, train allies, steal resources and switch weapon would be the best choices. Climb walls would be useful, but currently very few people turtle, so it is useless for most maps.
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