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I was curious as to what advantages everyone saw in other races recruiting the kroot? Personally, I found the kroot to be of exceptional value in my DE where they provide the meat shield for my WWP carries thanks to their infiltration (allowing me to not have to worry about wether or not my WWP carrier should fleet after my troops roll a 1; and allows me an initial barrage of fire that I was lacking when fielding hordes of warriors), and improved cover save (which greatly increases my survivability because I hated running warriors through cover). They also offer a radically different type of close combat from warriors (having better strength and dual weapons as opposed to the insane initative) which helps keep the DE from becoming boring and provides me with more options.
Everything I have told you, even this, is a lie.
Kroot are great. The only detractor is the expense. A full squad with 12 hounds is over $250. Those stupid hounds are expensive, but extremely effective.
I have played my DE against Tau. My only road block are the darn Kroot. I take raider squads and no wytches. It takes two squads about 2 turns to finally destroy some kroot.