Hey Dee, I started to mess around with your mod, it feels so great to add a whole new mechanic to the game. excellent work!

Testing:
I activated the "filthy Lucre" Perk, killed 1 warbeast and spawed a ZOMBIE_ANCIENT_CHAMP that gave me 150 Fame but 0 gold... As I followed your instructions 1 by 1 it worked. As i killed a warbeast activated the Perk and killed 2 champs, no gold then I de- and activated it again, killed more champs and gained the bonus...
Result:
The Fametogold isn't the best thing for testing because you cant see if its applied or not. better use playeraffix for testing.

I created a Perk myself using PLAYERSTAT and PLAYERAFFIX as reward but couldnt get it working.

Spoiler: PLAYERSTAT (hover to show)

[TASK0]
      <STRING>TYPE:PLAYERSTAT
      <INTEGER>COUNT:10
      <STRING>STAT:CHARACTER STEPS TAKEN
   [/TASK0]

I'm using the Player Steps Taken Stat what is a static stat so I created a stat with that name and the Predefined_Int for dynamic use. still so result.
I changed back to PLAYERKILL and got the affix applied (PERK_ROLLOVER.LAYOUT stays the same => hard to see if applied or not!)

I modded your PERK for testing and found something interesting:

Spoiler: Filthy Lucre (hover to show)

[PERK]
   <TRANSLATE>NAME:Filthy Lucre
   <TRANSLATE>DETAILS:|cFF0467FBKill 1 Warbeast.\nPerk: Converts each point of Fame earned into gold.|u
   <STRING>ICON:skillicon_barter
   <STRING>ICON_DISABLED:ig_skill_empty
   <INTEGER64>GUID:-3134059470467886625
   [TASK0]
      <STRING>TYPE:PLAYERKILLS
      <INTEGER>COUNT:1
      <STRING>UNIT:Warbeast
   [/TASK0]
   [REWARD0]
      <STRING>TYPE:FAMETOGOLD
      <INTEGER>FAME:1
   [/REWARD0]
   [TASK1]
      <STRING>TYPE:PLAYERKILLS
      <INTEGER>COUNT:2
      <STRING>UNIT:Warbeast
   [/TASK1]
   [REWARD1]
      <STRING>TYPE:FAMETOGOLD
      <INTEGER>FAME:2
   [/REWARD1]
   [TASK2]
      <STRING>TYPE:PLAYERKILLS
      <INTEGER>COUNT:3
      <STRING>UNITTYPE:MONSTER_CHAMPION
   [/TASK2]
   [REWARD2]
      <STRING>TYPE:FAMETOGOLD
      <INTEGER>FAME:3
   [/REWARD2]
   [TASK3]
      <STRING>TYPE:PLAYERKILLS
      <INTEGER>COUNT:4
      <STRING>UNIT:Warbeast
   [/TASK3]
   [REWARD3]
      <STRING>TYPE:FAMETOGOLD
      <INTEGER>FAME:4
   [/REWARD3]
[/PERK]

Now the progress showed 0/10, this is the total count 1+2+3+4 = 10 even if there are only 4 tasks and rewards...
After killing 1! warbeast I ended up with 3/10 => there are 3 tasks containing kill Warbeast
After killing more I ended up 7/10 => 1+2+4
=> to get 10/10 I need to kill the 3 champs

This shows you can set up multiple different tasks to get the rewards. TaskX and RewardX are not bound to each other - i.e. for 2 "progressions/counts" you get 2 rewards. I believe the only thing you can set is the order you receive rewards. placing the same task multiple times makes less sense since "progression" will show wrong numbers until u hit the max count of that task.
Playerstat needs testing... or I'm just dump setting it up.

this is gettin funky!

Any progression on the CONDITIONAL block?
I still cant get the PLAYERSTAT working. Here's my setup:
[TASK0]
<STRING>TYPE:PLAYERSTAT
<INTEGER>COUNT:1
<STRING>NAME:CHARACTER STEPS TAKEN // Statname to refer to //
<INTEGER>VALUE:3 // Stat Value // testing
<FLOAT>VALUE:5 // Stat Value // testing
<FLOAT>MIN:2 // Min Stat value // testing
<FLOAT>MAX:2 // Max Stat Value // testing
<FLOAT>CHANCE:50 // Chance // testing
<STRING>WATCH_TYPE:GREATER THAN // watch type
[/TASK0]
none of them applied the reward. I've changed the stat to check if something's wrong with that, no changes. Running out of Ideas

I'm using the Player Steps Taken Stat what is a static stat so I created a stat with that name and the Predefined_Int for dynamic use.

I tried another dynamic stat that is shown in the player effect and stat watcher
I'm sure its not the stat but the code...

so they could be used as a requirement?
lets say perk2 has a CONDITIONAL that checks for perk1 is completed/active (whatever) to actually appear in the list?
The ACTIVECONDITIONAL could be an outer block for the TASK/REWARD? so after completing the perc automatically gets activated...

no progression over here

Well I've spent a ton of time on a brute force technique trying every possible permutation of tags and code in a bid to get the QUESTCOMPLETE and PLAYERSTAT types to work for tasks but to no avail

So I've resorted to asking Runic, will keep you posted on what they say but I'm not entirely hopeful. Failing them throwing us a bone here, we're restricted to PLAYERKILLS types of tasks unless more trial and error can get the other types working.

I know Runic abandoned this whole perks thing so it may be that the code is incomplete and simply won't work, but I'd find that hard to swallow given how much of this residual stuff still works just fine plus they re-coded it when going form TL1 to TL2. Fingers crossed!