that looks a bit like your resin is significantly offgassing during the cure. degassing at the beginning of the cure often won't help in these kinds of situations, because the gas doesn't form until during the cure reaction. higher pressures might make the bubbles small enough that they don't form on the outer skin of the cast, but it looks like your pressures might already be pretty high as it is, from the isometric look of the bubble distribution.
an advanced technique that i've seen used for very volatile thermosets is alternation between pressure and vacuum. the basic idea is simple, but in practice it's quite tricky to pull off. basically, you are pressure casting, so you set your pressure as necessary, and then periodically (the time intervals you will just have to guess-and-check over multiple casts) you apply vacuum, attempting to coalesce the bubbles that have formed and evacuate them from the mold. you then quickly bring the mold up to pressure again.
note that this is especially tricky because, as the cast cures, it gets increasingly viscous (until eventually it becomes a solid), and hence more difficult to move bubbles around in. however, when you apply vacuum to the mold, the casting material may want to come out the mold as well, depending on viscosity at the time of alternation and the way the sprues are set up in the mold. so this is definitely an "everything else has failed" sort of technique.
one thing to check before you go screwing around with your workflow is to see what the bulk cured material looks like; cut the casts open, don't just observe the surface. if your bubbles are all at the surface, for example, then it may be that there's some weird nucleation on your mold surfaces or just not enough pressure early on in the cure. if the material is uniformly bubbled, then it may very well be the scenario i described above. you may also want to map out your casting material's cure schedule. run partial cures to increasingly longer timings and observe how viscous the material at each stage in the cure. as it reaches full cure, you'll also be able to see where and how the bubbles start to develop, as if you had a window into your mold.
