well it's a bit of a guess but I'd say the combination of VMware and 2 cores just doesn't provide enough workers.

There's some things you could try: disable parallelism, enable fibres.

I'd actually suggest you try to test on a physical box and/or get more cpus.

The whole thing about performance is that it's rerely one golden bullit. For example if your transactions/batches can't finish quick enough then you'll get queuing/blocking etc. this could be that your transaction log drive can't write fast enough ( quite likely on VMware which I've found absolute rubbish under load ) what you might be seeing is the after effect rather than the cause - blocking will ramp up threads, serialisation of stored procedures ( serialised execution plans ) can cause queuing the same. You may not have enough memory, disks may be too slow .. really tricky to know for sure.