you can summon new bats every few seconds with no problem as long as you can hit something . who cares about the 6 minutes? it could have been 2 minutes or 1 hour , it would have made no difference . have you played a batsin recently ?
in Sigma you get all the bats army out very quick compared to older versions when you had to summon them one by one . it's much easier to play now from this point of view
also , the claws have a high attack rate , so most of the time it's hard to predict with exactity which charge you got on (mostly if you are in the middle of a fight , surrounded by enemies and you can't see how many charge whirles you got around your character - or if you get into hit recovery for a second without noticing) , and sometimes you get new summons out weather you want to do it or not , so the army is always around . the 6 minutes thing does not affect the build in any way . i've streamed one of those today trough early game up to around level 104 , in case someone's curious to see how it performs :
https://www.twitch.tv/chucknorised/videos