I should say that in my current game stage (midgame) the skill is not weak, and that I have no first hand data on endgame yet. In the earlygame it is FAR stronger than BoTB and costs 0 story points to use, and in the midgame it lets me have a wide effective build with again 0 story points and saves me a good amount of money (I currently have 13 ships, so the skill is saving me ~25k per month in officer cost).
One way to buff it, should that be desired, would be to make unofficered ships 'count' as officered for the purposes of other skills.
Another possible way to take this skill would be to make it stronger in some way but have it come with the downside of reducing max officer count.
Just not being a capstone would be nice for variety IMO, can go lighter on leadership and get more from the other trees.
I think having it not be capstone is interesting: maybe the same tier as the 2 officer boosting skills? It is the "other" path compared to officers after all.
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You are already paying for SD by not using an officer, that's a big enough drawback.
While this is something I'm doing as a fun/challenge run, this isn't a thing with the skill normally. In the early game it lets all ships have better officers than they'd normally have; in the midgame it gives 'decent' officers on as many ships as you want while saving lots of money; in the endgame it lets you use unofficered ships at all, and at a discount so if the officers are in smaller ships then their effect is less "wasted". But none of those require not using officers at all and for things like wolfpack builds the player might even take extra officers while still using SD!
I think for the current capstone version damage control could be replaced with something generally useful (gunnery implants, field modulation), and it'd still be weak.
Most small or high tech ships will just die the moment they lose shields with or without damage control, it's barely better than no skill for them and isn't that hot even for the rest.
I think you are undervaluing damage control - for high tech not the damage resistance part (an extra 33% hull on something with 2k just isn't very much) but the weapon/engine repair speed. Nothing kills a small ship faster than losing engines! For low tech they can receive a good amount of hullpoints (2800 extra hull on a reinforced hull enforcer brick for example), and the repair speed means they don't stop firing for as long, so the enemy can't disable and ignore as much.
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Now I haven't reached endgame yet so this is theorycrafting, but one thing that is really standing out to me is that, because I don't have an officer on a ship that might be mismatched with another, and because I'm not using S mods on them, losing ships (especially frigates) in the endgame basically won't matter. Example: Say if I go punch an ordo and lose 4 SD wolves in the fight (out of say 16, which would cost 64 DP). Recovering them with a story point is 100% bonus XP if I feel like it, but its only like 20k each just to replace them. And a non-S mod recovery that gives a few D mods is 'fine' and amortizes that cost. Compare to an S mod cruiser or something where if it gets a D mod the repair build is in the 100k+ realm and replacing it costs net story points.
As I play more I'll see how that pans out!