I always enjoyed it when skills and talents could supplement each other( by strengthening their effect, compensating their disadvantages and helping to fullfill their activation requirements). Character creation and overall strategy becomes more interesting and often innovative or unusual concepts(character builds and strategies) can be created. In fact for example when I played Diablo2 i never reached a very high level, but I enjoyed and spend quite some time on coming up with excentric or largely unused char concepts and try out if they could function.(unfortunately many skills became useless in nightmare and many skills had no reason to be raised past lvl 1(teleportation(mage skill), telekinesis(mage skill), hunger(druid skill) etc).(Titan quest dealed with that problem in an interesting way but still lacked a little bit potential for unexpected combinations) For the same reason of combining stuff Ragnarok Online (RO) was so enjoably, although skills were limited to class there were quite some number of builds that could be realized exspecially with second classes.(Its for the reason that Ro2 skills seem to lack that combability that turned me away of the game although i had great hopes in it) So what more games and concept that have this combination aspect do you know and what more ways of skills supplementing each other. (Games like Saga of Ryzom that let you actually construct your own skills I think are actually a subform of this combination approach)

I don't know if you've played diablo 2 recently but they added a "synergy" aspect to the skills, where hard points into firebolt add's % dmg to fireball and meteor.

Also, there IS a build that maxes telekinesis. Memory Staff Energy Shield Sorceress. I actually have a perfect 20 Damage Reduction / 20 Magic Damage Reduction Gladiator's Bane Unique Wire Fleece. The idea is to max Energy Shield, and get it to lvl 40 with +skills (memory staff with +3 base energy shield), and telekinesis reduces the damage taken to your mana with each hard point. Since the Damage Reduction and Magic Damage Reduction take place before your resists, but AFTER the 1/20 reduction from energy shield, a small amount of DR/MDR can nullify over 500 damage per hit. You do need a lot of mana and an "insight" runeword mercenary. And mana burn is bugged so it takes ALL your mana.......otherwise it would be pretty much invulnerable.

Yeah I know about the synergy it was actually an cool idea so skill could support each other, but builds like the one you describe are so incredible item dependant, actually never understood how people could get enough +skill items to actually get skill level 40, well but as I said was not hardcore enough to ever actually level till hell and past lvl 40-50(which i think was the area my highest chars ever got to).
One thing I always wanted to try was use the ice armors as a means of passive attack, but I think even with synergies they did not get enough damage for that to succeed.(even if you added other passive skills like thunderstorm the damage was not great enough)
(oh and another thing I always wanted to have is a Druid built where I max hunger, but the Druid had just no skill that consumed enough mana or life for that to be useful,atleast not while transformed)