Again not true, PDT and MDT at best take up 7-8 slots, Nuking gear is a full static set of 16 slots, TP is a static set of 16 slots and WS depending on your WS of choice can take up 16 slots (if you use /BLU and Sanguine Blade your WS set is the same as your nuking set for the most part).

Where RDM sets get really in depth is group play (at least in the past) where you had enfeebling MACC, enfeebling MND potency, Enfeebling INT potency, Nuke MACC, Nuke DMG, Healing MND/Skill/Potency.

You don't need to carry every set with you when soloing, you take the tools with you that you need. If you are /BLU you don't need a nuking set because you are more than likely never going to nuke, unless you want a head start and chainspell nuke early (which increases kill speed but also greatly increases your chance of dieing having to blow convert early in the fight while at the same time decreasing MOB HP enough that it will use TP moves more frequently.)

Hell with most stuff a RDM can solo outside of abyssea you need at best 2-3 sets of gear, you will know before hand how you will take out a mob, so you bring the gear you need and leave the rest at home. Soloing has come a long way since Avesta. Rog for example was a solid soloer who brought /SCH into the mainstream, Xenith was very successful at soloing as /BLU. Both these choices involve different gear sets, but in a solo atmosphere you don't need those 4th 5th 6th sets of gear, especially now that we over level anything a RDM can solo outside of abyssea, in some cases by 10 or more levels.