For me, I run a level 60 with one level 29. Never used party sync. If I had an unlimited budget and desire, I'd run four level 29s with my level 60. But I'm in cruise control WoW mode these days and two accounts is enough.
I could solo WoD dungeons with the level 29, but I prefer to plow through easily on the 60 and collect gold and level 26 and 36 green wrist/gloves/belt/boots/rings for future projects.
I've been running just WoD Bloodmaul Slag Mines for i112 gear, BRD for the i112 cloth helm with socket proc, Gnomeregan for i86 versa ring with socket proc, and wotlk Azjol Nerub for i86 trinket the past 2 weeks. Also started gearing my level 30s with Sunwell gear, but that's another story.
As other threads have mentioned, i112 + socket + tert is not easy, and likely could take years to get. I think the chances were less than 0.5%. But base i112 gear is fairly obtainable (typically see 1-2 warforge every couple dungeon runs). Personally, I think base i112 is more than enough for pvp and pve. Any socket and tert is overkill and gravy.
The high level toon's drops stay at level 40 required.