Yeah, you're right, Beast+Might is way cheaper and delivers the same +ED%, more or less. In most cases, this would be a better choice.
But there where some reasons to go for a different approach:
This build is based on LAZINESS. So I strived for getting as many high-ranged auras as possible while being as safe as possible as well.
The desert guy was the first one I hired, of course. But his performance turned out to be quite embarassing for this kind of playstyle (relaxed, no CE, no aggressive telestomping). He got blocked most of the time by that huge army, desperately trying to find a route to the enemy.
The rogue on the other hand is actively engaging in combat. And with all that aura +ED%, she does some damage. Inner Sight is a worthy replacement for Conviction which fulfils the same purpose. The whole army is literally centered around her. She can wear Cure and Bramble (both having very bad combat stats) and still stay safe (Faith gives +15% allres!). This doesn't work well with a melee merc.
Then, Beast has a very low range of 12,6 yards, putting the Necro in danger while Might (32 yards!) allows to stay aside the rogue in safety. A good Faith has around 16 yards which is enough to cover most of my troops.
Last but not least, Last Wish gives me a chance to proc Fade and a nice magic find bonus where Beast has nothing to offer but the Fanaticism aura (the strength bonus is irrelevant due to Enigma).
Beast is absolutely made for a Summoner Druid who makes use of shapeshifting and actively joins the fighting now and then.
DasNarf
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