Yes, just the most levels. So a 6/6/8 build would get the past life of the level 8 class. In the case of a tie, the classes are chosen based on alphabetical for the core classes, then the order the classes were added to the game.
http://ddowiki.com/page/Past_Life_Feats
Here's another on my theory-doc for my ranger PLs ... it ends up Arti 6 / Rogue 7 / Ranger 7 with a ranger past life.
1 Rogue 1 - point blank shot
2 Arti 1
3 Arti 2 - rapid shot
4 Arti 3
5 Arti 4 -quicken
6 Arti 5 - precision
7 Arti 6
8 Rogue 2
9 Rogue 3 - precise shot
10 Rogue 4
11 Rogue 5
12 Rogue 6 - improved crit ranged
13 ranger
14 ranger - rapid shot (swap rapid for dodge with Fred)
15 ranger - improved precise shot
16 ranger - precise shot - WASTED FEAT
17 ranger
18 rogue
19 ranger
20 ranger
In the early levels I use a master-craftmanship BTA screaming of bleed, then a holy of bleed for most content. I also have a ghost touch of greater incorporeal bane and an anarchic of greater construct bane - but these you could replace with a holy of ghostbane and/or disruptor / smiter.
Greensteel-wise, I made a radiance. I'm toying around with making another one or two - that would be a 3xPos for undead killing and/or an ice one - but I breezed through last life with the radiance, so that's just maybe greedy on my part.
Rune arms I use Strinatis for lower levels (to break barrels), Hand of Tombs later (breaking barrels, disrupting) and a few other for their imbues. Later levels I mostly use a master-crafted Tira's Splendor but have the other BTA ones.
My rad2 (radiance, blinds targets on crits):
http://www.iro.umontreal.ca/~delalle...ming,__flaming
Pos3 (greater disruption):
http://www.iro.umontreal.ca/~delalle...__good&altar=3
Others enjoy Sundering Ooze and Trap the Soul repeaters.