It would be of interest to me to find out which cervids and caprids have been singled out as "phase-out" populations.
The Caprid TAG has been inoperative for several years now, and so there is really no single direction with these species ... it is mainly based on curatorial whim. With San Diego divesting most of their (extremely extensive) caprid collection, the future of these species is highly questionable ... only takin seem to be expanding right now; markhor are doing not-too-badly, as are bighorn sheep, goral, and serow, but ibex of all sorts (with the possible exception of Nubian ibex) are in decline (lots of questionable genetics among these).
With the deer, the big pushes are for increased holding of Bactrian wapiti, and Eld's deer. Other species (hopefully) on the increase are pudu, Barbary red deer, white-lipped deer, Calamian deer, Pere David's deer, and tufted deer.
It is important to remember that TAGs are just that -
Advisory groups. Ituri's hierarchy is very theoretical, and TAGs would LOVE it if zoos planned their collections this way (the RCPs are, as okapikpr says, almost a marketing tool). However, much (all) of it is left up to the individual zoos. DERP species are included in RCPs principally because there is a lot of institutional interest and/or numbers in zoos. SSP/PMP/DERP programs are assigned based on numerical rankings (based on conservation need, number of founders, exhibit appeal ... listed in the Antelope TAG document), which lends a bit of objectivity to the process.