Hi, as PVE multiboxer, ill share my personnal experience on that :
I used to farm Gold in PVE with multiple of 10char team able to run raids weekly on top of the weekly WG quests.
Naxxramas10 was the raid giving the more gold / boss and abviously the easyest, overall the t7 raid tier is good and not hard to farm. Flat gold, DE and emblems each boss for each char give very good result for an under 1hour run (skip thaddius id you arent confortable with multiboxing raiding). To make it simple numbers : even if you cant kill few boss, naxx10 is 5k gold, 20+ epic DE, 100+ EoT, just from boss (looting trashmobs was too long and boring for me). TOC10 is a 20min run with decent emblems/loot value (if im correct toc give 3 eot/boss, 15for the run/char : 150eot), VoA is also a 15mn run with good value. Ulduar is fourth in rentability, but more enjoyable imo.
25man raids give more loots but not really more gold per boss, are harder and require more decent char ; but if you can handle it too its also to add on list.
Once your main team atleast is confortable with ICC and get the t10, you will also make decent gold with the eof farm and saronite.
The 3 miniboss before Halion are also easy to learn and handle and give free EOF (Halion as 10boxer is another story abviously)
Also the ICC weekly with luck give sometime 1 or more choker from the bag, wich sell for 15k+, with 10 char doing 10 and some 25, i used to get a lot of good boe from that quest.
Dont even think doing gold by farming trash before marrowgar.... its a terrrible idea with low profits (those mobs give low gold, and almost all those boe got no value on market).
That playstyle was giving me a very good gold income without really "farming" but just playing my way, i've been able to gear a lot of teams and trade gold for coins multiple time/week. More and more whit more teams, in the limit of your playtime/week
PS : Im afk from Icecrown since 1year or 2, maybe some changes happened since that
Gornak