This was posted by zeth07 before the Echo nerf went live. This should give you a rough idea of an endgame server. Giglamesh has more people that have cleared T13, but due to its higher population, the percentage is a little skewed. Most of the "NA World-First" raiders belong to Giglamesh, such as DNT and Collision.

1 Excalibur (NA) (LEGACY) 4.80% 2 Gilgamesh (NA) 4.50% 3 Hyperion (NA) (LEGACY) 4% 4 Behemoth (NA) 3.50% 5 Sargatanas (NA) (LEGACY) 3.50% 6 Adamantoise (NA) 3.10% 7 Ultros (NA) 2.90% 8 Leviathan (NA) 2.80% 9 Cactuar (NA) 2.70% 10 Midgardsormr (NA) 2.30% 11 Balmung (NA) (LEGACY) 2.30% 12 Diabolos (NA) 1.70% 13 Exodus (NA) 1.70% 14 Coeurl (NA) 1% 15 Goblin (NA) 1% 16 Malboro (NA) 0.80% 17 Lamia (NA) 0.80% 18 Siren (NA) 0.80% 19 Famfrit (NA) 0.80% 20 Faerie (NA) 0.70% 21 Brynhildr (NA) 0.60% 22 Mateus (NA) 0.50% 23 Zalera (NA) 0.30% 24 Jenova (NA) 0.30% NA Average = 1.97% (EU) 1 Ragnarok (EU) (LEGACY) 3.90% 2 Odin (EU) 3.20% 3 Moogle (EU) 2.90% 4 Shiva (EU) 2.30% 5 Cerberus (EU) 1.40% 6 Phoenix (EU) 1.20% 7 Lich (EU) 0.30% 8 Zodiark (EU) 0.10% EU Average = 1.91% (JP) 1 Chocobo (JP) 15.60% 2 Garuda (JP) 13.90% 3 Mandragora (JP) 13.80% 4 Carbuncle (JP) 13.70% 5 frit (JP) 13.20% 6 Bahamut (JP) 13% 7 Tiamat (JP) 12.60% 8 Alexander (JP) 11.90% 9 Atomos (JP) 11.60% 10 Titan (JP) 11.20% 11 Fenrir (JP) 11% 12 Ramuh (JP) 11% 13 Anima (JP) 10% 14 Ixion (JP) 10% 15 Aegis (JP) (LEGACY) 9.80% 16 Gungnir (JP) (LEGACY) 9.80% 17 Durandal (JP) (LEGACY) 9.40% 18 Hades (JP) 9.20% 19 Ultima (JP) 9.20% 20 Valefor (JP) 8.80% 21 Masamune (JP) (LEGACY) 8.60% 22 Ridill (JP) (LEGACY) 8.30% 23 Typhon (JP) 8.20% 24 Unicorn (JP) 8.20% 25 Tonberry (JP) 7.30% 26 Kujata (JP) 6.30% 27 Pandaemonium (JP) 5.80% 28 Belias (JP) 4.10% 29 Zeromus (JP) 4.10% 30 Yojimbo (JP) 3.20% 31 Asura (JP) 2.90% 32 Shinryu (JP) 2.80% JP Average = 9.33% OVERALL: 1 Chocobo (JP) 15.60% 2 Garuda (JP) 13.90% 3 Mandragora (JP) 13.80% 4 Carbuncle (JP) 13.70% 5 Ifrit (JP) 13.20% 6 Bahamut (JP) 13% 7 Tiamat (JP) 12.60% 8 Alexander (JP) 11.90% 9 Atomos (JP) 11.60% 10 Titan (JP) 11.20% 11 Fenrir (JP) 11% 12 Ramuh (JP) 11% 13 Anima (JP) 10% 14 Ixion (JP) 10% 15 Aegis (JP) (LEGACY) 9.80% 16 Gungnir (JP) (LEGACY) 9.80% 17 Durandal (JP) (LEGACY) 9.40% 18 Hades (JP) 9.20% 19 Ultima (JP) 9.20% 20 Valefor (JP) 8.80% 21 Masamune (JP) (LEGACY) 8.60% 22 Ridill (JP) (LEGACY) 8.30% 23 Typhon (JP) 8.20% 24 Unicorn (JP) 8.20% 25 Tonberry (JP) 7.30% 26 Kujata (JP) 6.30% 27 Pandaemonium (JP) 5.80% 28 Excalibur (NA) (LEGACY) 4.80% 29 Gilgamesh (NA) 4.50% 30 Belias (JP) 4.10% 31 Zeromus (JP) 4.10% 32 Hyperion (NA) (LEGACY) 4% 33 Ragnarok (EU) (LEGACY) 3.90% 34 Behemoth (NA) 3.50% 35 Sargatanas (NA) (LEGACY) 3.50% 36 Yojimbo (JP) 3.20% 37 Odin (EU) 3.20% 38 Adamantoise (NA) 3.10% 39 Asura (JP) 2.90% 40 Ultros (NA) 2.90% 41 Moogle (EU) 2.90% 42 Shinryu (JP) 2.80% 43 Leviathan (NA) 2.80% 44 Cactuar (NA) 2.70% 45 Midgardsormr (NA) 2.30% 46 Balmung (NA) (LEGACY) 2.30% 47 Shiva (EU) 2.30% 48 Diabolos (NA) 1.70% 49 Exodus (NA) 1.70% 50 Cerberus (EU) 1.40% 51 Phoenix (EU) 1.20% 52 Coeurl (NA) 1% 53 Goblin (NA) 1% 54 Malboro (NA) 0.80% 55 Lamia (NA) 0.80% 56 Siren (NA) 0.80% 57 Famfrit (NA) 0.80% 58 Faerie (NA) 0.70% 59 Brynhildr (NA) 0.60% 60 Mateus (NA) 0.50% 61 Zalera (NA) 0.30% 62 Jenova (NA) 0.30% 63 Lich (EU) 0.30% 64 Zodiark (EU) 0.10%