Redoing your math... 25 hits, then 21 more on the reroll. Just shy of 8 wounds, which is almost three wounds off a hive tyrant. Of course, more than 12" away, you still knock an average of 2 wounds off...

Within 12 inches, bring it down is a slightly better order than first rank, second rank.

50 conscripts & 2 characters shoot 102 dice, hit 17 times. The divination reroll makes that 14 more, so 31 hits.

Out of those 31, 5 wound, and then on the reroll 4 more wound, for 9 wounds, then about 3 wounds come off the hive tyrant.