Home Sweet Sewer seems to be an optimal test case for anyone, player or Turbine employee, who wants to try and duplicate what players reporting issues are experiencing. It has exactly six (6) mobs, in a relatively small contained area. The mobs are not "dancers" like kobolds - they wont jump in and out of close range. They swarm and stay as close to you as possible. There are ample spaces that are flat, and there are boxes/steps available for testing whether different height/z levels are affecting the outcome.
Test scenario 1: remove all guard items; don't aura. run in and gather the six dogs around you on a flat floor space (easy to find, e.g. on the west corridor). Stand still. Wail.
Expected outcome: 3 ticks where we see two of the dogs either (1) die, or (2) save and enervate/drain; we expect to see zero spell penetration failures.
Actual outcome: about 2 out of 10 tries, I saw all six dogs die. On every other attempt there were at least 1 or 2 dogs left alive; however in only one or two cases were they level drained. I think I saw a blue hexagon once in all tests; what I did not see were the expected enervation/drain indicators that should have occurred *every time* the dogs saved (which I assume, could only happen on a roll on 20 and should have been very rare anyway).
Test scenario 2: remove all guard items; don't aura. run in and gather the six dogs around you while standing on the top steps of one of the "holes" in the corridor walls. The idea it to elevate your character above the dogs. Stand still. Wail.
Expected outcome: 3 ticks where we see two of the dogs either (1) die, or (2) save and enervate/drain; we expect to see zero spell penetration failures.
Actual outcome: pretty much the same results as scenario 1. Frequently leaving one or two dogs alive, almost always with no observable indication that they had saved or that the drain-on-save effect had occurred.
Test scenario 3: remove all guard items; don't aura. run in and gather the six dogs around you but run back and forth on flat floor space in a corridor. Turn around, run back to the dogs, then wail on the run. The idea is to duplicate your (presumably) usual behavior in active combat which is movement and jumping over/around mobs.
Expected outcome: 3 ticks where we see two of the dogs either (1) die, or (2) save and enervate/drain; we expect to see zero spell penetration failures.
Actual outcome: This time, never saw all six dogs die. Saw a couple drain indicators, no blue hexagons, and generally left either 3 or 4 dogs alive, but sometimes 2 or 5. Now I was careful to stay in the usual range even while moving and jumping - certainly it's easy to stay in almost touch range of at least 2-3 of the dogs but keep moving.
Conclusion: I realize these tests aren't perfect but they're about as good as anything players can do. Wail is still not working like pre U17. Negative correlation to different relative z levels. Positive correlation to movement while the spell effect is ticking. Positive for save indications not appearing consistently and drain-on-save not applying consistently. Speculating that maybe the random mob picker is sometimes assigning the same mob twice - so that when it dies, it's checked a second time anyway resulting in apparently less mobs being affected?
If anyone else would like to run into Home Sweet Sewer and give it a shot, please post results here.