There are no fights on normal mode that can't be done with more than 2 melee in the group. Cho'gall could get interesting with the add spawns, but there are no fights that I would consider un-doable. The few bosses which forced stacking of ranged dps to beat them were changed (heroic ascendant council for example killed your melee in seconds with chain lightnings until it was changed) so that those mechanics would choose a ranged target if one existed.
That being said, you can't expect to turn up with a totally wonky setup and expect to win. Fights on 10 man are designed with a 2/3 split in mind; this is evidenced by the presence of mechanics like interrupts on spells cast every 6 or 12 seconds, together with stuff that is better when taken by a player at range (magmaw lava pillars, maloriak iceblocks, the magical explosions at V&T etc).
Which fights in particular would you say favour ranged dps so much that taking melee would be a detriment to the progress of the raid?