HRMs - Still Redundant

I've never been a fan of using a HRM for distance training. Yes, HRMs do measure how hard one is working; however, there are too many determining factors that warp BPM in to an "impure" reading. I suppose there are few data outputs that are rarely complete pure, but what's the cause for all of the HRM hype?

Last January I started the new year with an open mind and a marathon on the brain. Thus, I committed to giving HRM training a whirl. I initially planned to use it solely for base training. The feature that beeps (REALLY annoying) if you get too high ensured that I kept a slow pace. [Background: early season, I tend to get hyped, train too hard and get injured.] After two months I figured I may as well keep wearing it.

I rarely use it as an intensity monitor during training (other than for long runs), yet I thought I could use it more for planning purposes after training. For example, I have ploted the corelation of HR (bpm) and pace (min/mi). The lower-right corner is the most desireable as it maximizes pace and minimizes HR (go faster for longer).

The above points and trend lines include runs that I wore a HRM (~65% of the time) for the below given distance ranges:
Navy: 10 mi or greater
Pink: 6 - 9.9 mi
Yellow: fewer than 6 mi

Clearly, the further I run the more the trend line shifts to the undesirable corner (upper-left), meaning I become more inefficient. On separate charts, I focused on the furthest outlying points from the trend line (for better or worse) to hone in on how I can maximize (minimize) my race efficiencies (inefficiencies).

Bad Outliers:
relatively out of shape (running beyond my current fitness level)
weather (hot/humid, snow)
terrain (hilly)
health (sickness)
lack of fuel (little/no liquids and food)

Good Outliers:
weather (cool/breezy)
steady pace (negative splits)
sufficient fuel (Gu and Gatorade)

I was crossing my fingers that more profundities be brought to light. Only the obvious was answered. HRMs - still stupid. And I schlepped that thing around for miles!