Between the Only War and Dark Heresy Second Edition, there was some serious cull in Talents section. I understand, that some of them were "broken" since their inception in DH1 (Fearless and Paranoia are probably the wordt offenders) and especially Fear, Insanity and Corruption reducing talents were lost, but many of them doesnt seem to be cut for any other reason than lack of space for new, Influence and Investigation Talents. I just wonder, would any of you have problems with players using Talents from Only War (for simplicity sake, as it has Aptitude system)? Do you have any old favourites that didnt make it but you still use them? And which ones should never be revived under any circumstances?

I made a document here to port many of the older talents over to 2nd edition some time ago. Some of them ended up in the expansions anyway, but here is this link

Clearly you can see I believe that most of them should have made it in.

I wholeheartly agree, as I wrote, I can understand why some of them have to go, to de-empasize the combat and "easy" Insanity/Corruption/Fear protection (Dark Soul was also no-brainer for example), but some of the more flavourful ones, which could be well used during investigations, such as Mimic or Heightened Senses are gone. As rule of thumb, I would allow almost any Talent from Only War (and supplements) if consulted beforehand. Combat Formation and Combat Sense got rolled into one Talent, but for example OW version of Hotshot Pilot could also be useful, it just need fluffy rename (and probably bump to the Tier 3, as Infused Knowledge) as it is different from DH2 Hotshot Pilot from Enemies Without.

I also consider using Talents from older, pre-Aptitude lines, as they could very elegantly represent various rather specific Alternate Career Advances.

A number of them were marginal at best, such as the aforementioned Mimic and Heightened Senses. What's the point of making a separate talent as a rules permission to do something that's already likely covered under a skill or characteristic? Others just weren't worth it if you weren't using the old restrictive charts (OW Hotshot Pilot costs about the same as just buying the other two Operate skills at +0, and the extra DoS is of limited benefit), or weren't worth it in general (Decadence and Orthoproxy). And finally some needed notable consolidation (two-weapon talents and called shot talents among them) because no one in their right mind was going to only take one step in the chain instead of grabbing the whole set.

Obviously a number of talents were cut for space, because the first priority for the new edition of DH was to make a cloak-and-dagger/investigation game in the 40K setting. But for every talent that was cut for space, I'll wager you that at least one other was also cut because it wasn't actually meaningful to characters.

Since we seem to agree that most of these talents were cut in favor of space and a more 'investigative' flavor. That being said, there's nothing stopping you from porting any talents from OW you might wish! If you need an excuse as to why they're not commonly available, perhaps the 'battlefield experience' gives the options for some different areas of development...

It is also important to keep in mind that the 2spirit" of many talents re-appeared in new talents with different names.

I'd just wish they'd take a whole bunch of the quite cool OW talents over into a DH2 expansion, to make them "official" DH2 talents.

or weren't worth it in general (Decadence and Orthoproxy).

Haha, I bought both of those on my last DH1 charcter. Totally worth it.