The racks would rarely be nearing physical capacity, but might actually bemaxedout in logical capacity due to power or cooling constraints at the rack level (the mantra to avoid creating hot spots in data centers has actually made floor and rack use a lot less efficient).
However, although there is a degree of choice in allocating where your skill points go in the midgame, by the end you should have maxed, or be close to maxing out, all four skills.