You've taken into account special relativity, but there is also general relativity to take into account. Gravity slows time. Near the Earth's gravity time is slowed. For GPS satellites, their 3.9 km/sec speed slows their clocks by 7 us/day, but the reduced gravity at 20,000 km speeds their clocks relative the earthbound clocks by 45 us/day. So in that case the effect of gravity is greater than that of speed, and they gain time relative to us.
Voyager 2 is going about 139 us/day slower than us due to it's speed. Once gravity is taken into account, I'd guess the result is somewhere around 82 us/day slower. Of course it's speed and the gravity it's experienced hasn't remained constant.