it is an interesting question, probably only the developers could answer it really well…
in the old game engine I use/used, in case of an RTS game with 400-500 bone animated human units, it resulted in significant performance boost not using separate “Tick” functions provided by the engine for all characters, but setting them in one custom loop in one main Tick function, and also using similar animation positions for as many units as possible (being in similar anim state, like idle/move). It can be very different with UE4 (e.g. currently my GPU seems to be the main bottleneck in my PC), so I will spend some time with it in the following weeks (and with the performance tools)…