"damage_all_in_hold" effects units that are in garrison or HT.
T-34/76 might have higher reload but it start firing faster with veterancy. Actually if one compares to Ostwind T-34/76 cost about the same while being superior against most target that are not planes.
One of the many problems with Ostwind and it's performance is that for the same price soviets can have t34/76 which is superior in everything compared to Ostwind. Only thing T34/76 can't do is shoot planes.