if we're talking about club music here:
you need to remember that because they have so much low freq / energy, anything you do with them has a drastic affect on the perception of the whole track. they can totally destroy the rhythm of any track, just with one badly placed tom on the grid. the reverse is also true. if its well placed, it can carry the whole track, and the track will sound pathetic without it.
so with this in mind, eq and level balancing is everything. even the perfect tom can sound wrong, if its a db too loud.
they should be given the same importance as your sub bass, and each should be tackled with the other in mind, as they both, together, create their own rythym