To the purpose of looking into replenishment specs and the effect of the Life Tap glyph I found an oddity.
Using these options:

#!simcraft max_time=300 optimal_raid=1
patch=3.1.0
warlock=3_13_55_w_Life_Tap_Glyph
level=80
talents=http://talent.mmo-champion.com/?warlock=030000000000000000000000000003220030003000000000000000005203215220331051035030351
actions=flask,type=frost_wyrm/food,type=tender_shoveltusk_steak/fire_stone/fel_armor/summon_pet,imp
actions+=/life_tap,glyph=1/curse_of_doom,time_to_die>=90/immolate/conflagrate/chaos_bolt/incinerate/life_tap
Warlock_T7_Gear.simcraft
glyph_immolate=1
glyph_conflagrate=1
glyph_life_tap=1
warlock=3_13_55_w_Inc_Glyph
level=80
talents=http://talent.mmo-champion.com/?warlock=030000000000000000000000000003220030003000000000000000005203215220331051035030351
actions=flask,type=frost_wyrm/food,type=tender_shoveltusk_steak/fire_stone/fel_armor/summon_pet,imp
actions+=/curse_of_doom,time_to_die>=90/immolate/conflagrate/chaos_bolt/incinerate/life_tap
Warlock_T7_Gear.simcraft
glyph_immolate=1
glyph_conflagrate=1
glyph_incinerate=1
warlock=0_13_58_w_Life_Tap_Glyph
level=80
talents=http://talent.mmo-champion.com/?warlock=000000000000000000000000000023020030003000000000000000005203205220331051335230251
actions=flask,type=frost_wyrm/food,type=tender_shoveltusk_steak/fire_stone/fel_armor/summon_pet,imp
actions+=/life_tap,glyph=1/curse_of_doom,time_to_die>=90/immolate/conflagrate/chaos_bolt/incinerate/life_tap
Warlock_T7_Hit_Gear.simcraft
glyph_conflagrate=1
glyph_immolate=1
glyph_life_tap=1
warlock=0_13_58_w_Inc_Glyph
level=80
talents=http://talent.mmo-champion.com/?warlock=000000000000000000000000000023020030003000000000000000005203205220331051335230251
actions=flask,type=frost_wyrm/food,type=tender_shoveltusk_steak/fire_stone/fel_armor/summon_pet,imp
actions+=/curse_of_doom,time_to_die>=90/immolate/conflagrate/chaos_bolt/incinerate/life_tap
Warlock_T7_Hit_Gear.simcraft
glyph_immolate=1
glyph_conflagrate=1
glyph_incinerate=1
It returned this ranking:
DPS Ranking:
25876 100.0% Raid
6559 25.3% 3_13_55_w_Life_Tap_Glyph
6488 25.0% 3_13_55_w_Inc_Glyph
6439 24.8% 0_13_58_w_Inc_Glyph
6433 24.8% 0_13_58_w_Life_Tap_Glyph
Looking at the mana graph for the 13/58 spec w/ the Incinerate glyph and I couldn't see the familiar traces of Life Tap spikes.

So I looked at the gains and it showed 7.8 Life Tap gains and over 27k mana returned. Seeing that Life Tap was clearly being used but not seeing any indication of it in the graph made me wonder if my results were invalid or even bugged. Insight would be welcome.