8 was a bit low, when you consider that a it had the same pop cap as a Panzergrenadier squad.
The Stug is also 8 pop, costs 10 fuel more than the T34/76, and the case could be made that it performs its role far better T34/76 currently does.
The reason 8 pop seems appropriate for the T34/76's current performance is that it results in a ratio of 3 T34/76s (24 pop total @ 8 pop) to every 2 P4s (24 pop total @ 12 pop). This also works out price wise (900MP/240FU for the T34s and 700MP/250FU for the P4s) and combat wise since 3 T34/76s are about what you need to take on 2 P4s. If you bump the pop to 10 then you have the same ratios but the Wher player has an extra 6 pop to spare for what is essentially an equal combat force.