Taking your Megaera logs as an example, while the dtps is similar, look at the amount of melee swings over 200k (i.e. burst events):
From the 10H log:
Code:
[22:07:53.095] Venomous Head hits Onzay 206218 (A: 3882)
[22:08:21.973] Venomous Head hits Onzay 279588
[22:08:23.641] Venomous Head hits Onzay 214512
[22:10:39.695] Venomous Head hits Onzay 268733
[22:10:40.945] Venomous Head hits Onzay 216192 (A: 3715)
[22:10:51.621] Venomous Head hits Onzay 210289
[22:13:09.317] Venomous Head hits Onzay 220663
[22:13:12.332] Venomous Head hits Onzay 206018
[22:13:14.339] Venomous Head hits Onzay 258946
[22:13:24.162] Venomous Head hits Onzay 275947
[22:13:26.160] Venomous Head hits Onzay 224930
[22:13:27.155] Venomous Head hits Onzay 238120
and compare that to the amount of melee swings above 200k for the 25H log:
Code:
[19:23:40.815] Frozen Head hits Bigpeat 239912
[19:23:43.252] Venomous Head hits Woodyhoss 213718 (A: 3903)
[19:24:52.110] Venomous Head hits Bigpeat 227987
[19:25:27.759] Arcane Head hits Bigpeat 259163
[19:25:29.798] Venomous Head hits Woodyhoss 238392
[19:25:40.782] Arcane Head hits Bigpeat 217015
[19:25:57.546] Venomous Head hits Woodyhoss 246977
[19:25:59.779] Arcane Head hits Bigpeat 211432
[19:26:00.391] Venomous Head hits Woodyhoss 226653
[19:26:39.614] Frozen Head hits Woodyhoss 254852 (A: 2109)
[19:27:16.361] Venomous Head hits Bigpeat 208526
[19:27:17.624] Venomous Head hits Bigpeat 261705
[19:27:50.919] Venomous Head hits Woodyhoss 216116 (A: 918)
[19:28:01.720] Venomous Head hits Woodyhoss 200315
[19:28:08.984] Flaming Head hits Bigpeat 216804
[19:28:26.578] Flaming Head hits Bigpeat 227561 (A: 26436)
[19:28:33.397] Venomous Head hits Woodyhoss 204588
[19:28:36.752] Venomous Head hits Woodyhoss 222203
[19:28:37.079] Flaming Head hits Bigpeat 241787 (A: 37004)
[19:29:21.545] Arcane Head hits Woodyhoss 239424
[19:29:21.710] Venomous Head hits Bigpeat 203534 (A: 3743)
[19:29:24.727] Venomous Head hits Bigpeat 253303
[19:29:36.489] Arcane Head hits Woodyhoss 224250 (A: 21514)
[19:29:40.536] Arcane Head hits Woodyhoss 204040
[19:29:42.576] Venomous Head hits Bigpeat 212221 (B: 90952)
[19:29:53.498] Arcane Head hits Woodyhoss 233691
[19:29:54.505] Venomous Head hits Bigpeat 209976 (B: 89990)
[19:29:56.526] Venomous Head hits Bigpeat 274521
[19:29:57.532] Arcane Head hits Woodyhoss 239533
[19:29:58.552] Venomous Head hits Bigpeat 244946
[19:29:59.526] Arcane Head hits Woodyhoss 236901 (A: 27957)
[19:30:01.538] Arcane Head hits Woodyhoss 242809
[19:30:02.553] Venomous Head hits Bigpeat 243505 (A: 2475)
[19:30:44.370] Venomous Head hits Woodyhoss 215072
[19:30:50.698] Frozen Head hits Bigpeat 275817
[19:30:55.467] Venomous Head hits Woodyhoss 248227
[19:30:56.405] Venomous Head hits Woodyhoss 238625
[19:31:01.620] Frozen Head hits Bigpeat 243956
[19:31:06.013] Venomous Head hits Woodyhoss 211279
[19:31:06.925] Venomous Head hits Woodyhoss 257460
[19:31:07.860] Venomous Head hits Woodyhoss 217687
[19:31:08.884] Venomous Head hits Woodyhoss 206991
[19:31:11.645] Venomous Head hits Woodyhoss 205209
You have the tank(s) taking a significantly larger amount of large melee swings than in ten man (12 in the ten man log, 43 in the 25 man log - almost four times as many). The high damage melee swings also only come from the green head in the 10 man log, which is the only head whose debuff stack increases melee damage taken by the target, the others enhance spell damage only. There are almost as many 250+k swings in the 25 man log as there are 200+k swings in the ten man log.
"Specials" rarely result in a tank death, because we plan for cooldowns to cover them. Like using unglyphed Divine Protection for breaths 1+3 at Megaera. If a special attack does result in a tank death, it is mostly due to a special+1 or 2 swings combination; i.e. the melee swing is what makes that moment dangerous, not the special.