Not actually true, PTG.
Believe it or not, Herc tasking (with the exception of arising ops and large deployment / recoveries) usually runs at about 70% of the AFT, versus Tri* and VC-10s which almost always overfly the AFT. At least that was the case about 3 yrs ago - don't have sight of any more recent data, so may have changed, but this was the historical norm.
I think Father Jack alluded to the real problem - the bulk of our tasking now is operational and requires either CR crews or additional post-grad quals such as Tac or NVG TALT, which reduces the pool. Add into this the numerous triv requirements such as IDT/IRT currency, and the paucity of such courses, and the pool shrinks further still.
In addition, when somebody falls over, or a short-notice requirement arises, it is extremely difficult to get someone ticked up from scratch to go, mainly due to this IRT bollox (they insist we do it and don't put enough courses on).
The upshot of this is that about half the crews on a squadron are doing 90% of the work, and back-to-back dets are not uncommon. I'd say we were more under-qualified than under-manned.
16B