When you fit both cams, the engine really would benefit from a bigger turbo at the same time, its not that you wont see *any* gains on a T34, like I said it just wont gain much.
With regards to if its the compressor or the turbine thats the real issue, its pretty much both really, they arent a bad match for each other on the T34 in the first place, although people do manage to get about 10% more power out of them when they fit the larger compressor wheel in what gets called a "T38" they end up losing response at the same time.
You're right that at the top end on the hotter cams it will pull better, but its only a case of that power drops off less, rather than power is gained, if that makes sense?
You end up hanging onto the gear for longer which makes it feel revvier, but in reality you've gained little in real world performance.
You mention that yours was still pulling hard at 7.8K, but I bet if you post the dyno graph you have not much over 200lbft of torque by then.

I see no point in trying to eek out a few extra bhp with different cams on a T34, when you could just change the turbo and unleash SO much more potential instead.

In general IME most tuners with the YB seem to find that a hotter inlet than exhaust gives a good balance, if you go too hot on the exhaust you end up with longer but weaker exhaust pulses at lower rpm, which tends to make the turbo then spool more lazily compared to the short sharp hit of the standard cam.