Research redirection: awfully overpriced. I think the base cost should come down to 20. You aren't getting any additional ships, just better fits into your fleet.
I agree that ARS hacking is overpriced right now. At 20 HaP base, you're looking at 100 Hap to hack 3 ARSs, and 250 for all 5.
Design Corruption: I never use this. I think a price of 10 would be about right.
I rarely use Design Corruption, but 10 HaP seems a little too cheap. At 10 HaP base, 4 corruptions is 80 HaP, 5 is 130. Against many AI types, 5 corruptions will reduce the AI to triangle ships until the endgame. 20 HaP may be better, but even leaving this at 30 doesn't bother me. In my mind, it's a way for the player to say "I HATE AI ZBombards, so I'm going to make sure it doesn't get any ever again!", as opposed to something done casually. I think the only reason to consider dropping the HaP cost of corruptions is because the AIs are independent.
Fabricators: 20 is quite cheap for a mkV cap. I would bump it up to 30 or 40, probably 30 because of limited selection.
Fabs are limited selection, and they are take-and-hold structures, unlike ARSs or Design Downloads. And on top of that, even in 100 star games you frequently get systems with multiple fabricators. When you consider that you cannot hack only a single fab out of a multi-fab system, your "free 1" goes away. I think 20 HaP is still right for this.
Sabotage: way too cheap. It can resolve really nasty situations for a small HaP cost, but I don't think that's the problem. The issue is when it kills structures which would give AIP, especially against an AI which seeds a bunch of said structures and additional data centers. I think that the base cost of 2x1.5^hacknumber is fine, but should have an additional cost of 1HaP for every AIP you avoid.
Adding the AIP cost to the HaP cost is an interesting idea, although it could make it hard to predict your final cost. My actual objection to this, though, is that it means sabotaging a distribution node would be more costly than sabotaging a Mk III Fortress or a Mk V Forcefield. And that's just not right.
That said, 2 HaP seems cheap to me, too, but Keith's argument that Draco18s found is fairly persuasive. If 8 is how many he thinks we should get for 100 HaP. If the base cost was raised to 5 HaP, that 6 sabotage hacks would cost a total of roughly 100 HaP.
Sensor Hacks are the big one I don't really understand. It takes 30 seconds to execute, only lasts for 35 seconds, doesn't hide shooting units, and costs 10 HaP base. 2:30 minutes of cloaking costs 130 HaP - about 4 k-raids, 2 ARS hacks, 4 fabs, or 2 design downloads. Cloaker Starships and Tachyon Warheads are superior in almost every way, so I simply do not see why a sensor hack would be useful.
My complaints are: It costs a lot of HaP for a temporary result, and it takes too long to start up, in addition to the high cost.
However, I've read several posts by other players that like the sensor hack a lot. This may be a playstyle arugument, then - not useful to me, but powerful for other players.
Finally, Advanced Production Facility hacking. Currently, these cost 100 HaP base. However, I almost think this should be increased to 150 HaP base. It's fairly easy to find one of the two (a Fac IV or ASC) that is somewhere that can be captured and defended, especially considering the B CSGs. However, finding one of each in good spots is much more difficult. But for a mere 100 HaP, I don't need to worry about it. And the ability to produce all Mk IV units is very powerful... Of course, right now the Fac IV is much more powerful than the ASC.