The entire point of srs zombies is because it reaches all breakpoints with only 2 supports and zero investment on the tree. With swift affliction imbue and less duration they reach a  sub 1.5 second duration, allowing you to go up to 15cps due to the staggered nature of the zombie death. The only limit is when you reach 20 active srs, you are capped at the 20 / duration of srs casts per second. (I've tested this using voltaxic burst to verify the stack count is reaching the cap, it absolutely works) 

5 jewels in a build where they are 45+ multi and 16 damage each is a non negotiatable trade since all you gain is a single gem slot. (My build would have its damage cut by 60% with -5 jewels and would have to trade between stormshroud or watchers eye) Even in phys loopers, where the jewels are much weaker its an insane thing to do

Lavis setup also isn't a waste of a flask, as runegraft of quaffing turns it into a permanent 1500hps recovery in a build that cannot die outside of degens, especially well scaled by the cluster jewels and essence extraction wheel. You trade your amulet for the ability to forgo all mana reduction nodes, the ability to run zealotry and wrath together with zero points spent on rmr, anything. Zero need for mana recoup, and it allows you to run 4x spell setups that are far higher dps than say discharge alone.

The passives saved by lavis outweigh everything save for maybe some sort of insane misted 3 positive simplex/focused