Those were among the last four I had as well (the fourth was Herald Volazj as I just could not get a shaman for love or money).

Make It Count: this is actually actually a lot easier than it seems. While Bloodlust helps on the boss fights, it's by no means required. Speed is mostly dependent on your group's ability to avoid trash and handle the bosses quickly. Do Make It Count with a 2-ruby, 2-amber, and 1-emerald setup that's agreed upon in advance. Clear your first platform, then the central ring, then the next platform, then fly *through* the central ring to get to Varos (this keeps travel time to a minimum). Only stop to clear 3 -4 dragons on your way between platforms. Don't bother looting Urom's corpse -- he won't despawn by the time you've dealt with Eregos. Doing this we typically end up with between 2-5 minutes left on the timer.

Emerald Void: Try this on a different run because you do run the risk of a wipe on Eregos costing you the Make It Count timer. We used a 1-ruby/4-amber setup and had 2 ambers always channeling while the 2 others spammed Shock Lance. Time Stop all of the enrages and fly clockwise or counterclockwise around the platform during the phase shift. The damage should be high enough to kill Eregos before he kills the ruby drake, although the person on the ruby should know what they're doing.

Less-rabi: Honestly, this achievement is still dependent on luck to a certain extent. Even if you count down to each Transformation attempt, any amount of server or player-side lag will usually screw you over, as will a badly-timed Stomp from him. Past 40% health you're looking at a 0.3 to 0.5 second cast Transformation, which is VERY hard to catch. So my only advice would be: a). bring a Bloodlust, b). bring very, very competent DPS, and c). bring multiple interrupts, have everyone count down and attempt to interrupt the last cast. And, if at all possible, have the second or last Interrupt be a Counterspell, which will give you 8 seconds of uninterrupted (pun!) DPS.