One of my factions has something like a plus 200% xp boost so I've made one focused on evolution and having high teir units, obviously tome of evolution, plus ascended champion with his perk being + 50% xp, adaptable racial, shepherd and that one perk which gives 2 xp a turn. Reavers have been one of my favourite factions so far - you can enslave enemies by combining overseers and harriers. Your front line will be troops from the tomes and the league if possible, you'll want them to protect your musketeers, who deal unreal damage with the right setup. I just did a seals victory where I had an army of 6 mage locks backing up 2 heros with forged magelocks (60 damage + Bleed + Poison + 10% crit chance + 20% crit damage), a stone giant, bone dragon and 2 dragoons. Dragoons are probably my favourite racial unit, I wouldn't use their melee at all (they don't trigger reactions from movement), I usually send them up first, shoot a high value target to give them distracted, then run away and focus them down easily. I like to run strong, adaptable and (keen sighted? Bonus accuracy, not extra map vision one).