In the beginning chapters, it showed the guides passing out from exhaustion. Right before he went berserk, it also showed the guides passing out from reverse guiding. I believe that “lost a lot of guides” just meant some are temporarily out of commission from attending to him, and their posts need to be replaced since lots of espers were out working. If he even let that sad excuse of a human being ex director live along with all of those abusive researchers, I highly doubt he would kill guides that were forced into the bureau and just doing their job.
Like I like them as a couple and all... But are we all just gonna ignore all the guides that died so he could replenish himself or what.