Just as it says.

Point is OW has many guardsman-good talents (and, if you want, any combat-based-good talents). So I wonder, how they are compatible with DH2 rules? It's essentially same system, so I believe it should be good but maybe I miss something?..

Especially the Leadership based talents since the amount in DH2 for non-elite advance characters is pretty abysmal.

OW is a very combat focused game and the character abilities are designed around making competent combatants. The ruleset is all but identical to DH2, so you could plug in the OW talents, but you would drastically change the focus of your game toward combat.

One of the characters in my party is exGuard sniper whose main job is tactical command to retinue ancilla and deal heavy damage to enemies. So it's his main goal - to be competent combatant and protect party (2 AAT psykers, tech-priest, charismatic rogue and fire-hearted preacher) from harm in the investigation.