I say Mega Blastoise is B-Rank worthy. It easily fits into bulky offense teams that need hazards out of their field. It has wide coverage in moves like Aura Sphere, STAB Water Pulse and Dark Pulse (which 2HKOS Shield Aegislash and Deoxys-D), and can surprise "checks" to the standard set with an unexpected Scald burn or Ice Beam on Dragonite.
Starmie for B-Rank. It has a negligible power loss from Mega Blastoise in exchange for more speed, the ability to hold any item, BoltBeam coverage, decent recovery, and can surprise Mega Venusaur that attempt to wall it with a Psyshock.
Highlight Donphan's placement in E-Rank. Outclassed by Excadrill in the offensive department because the mole can actually beat Mega Pinsir, outspeed and OHKO non-Balloon Heatran and Rotom-W that's uninvested and without a scarf, handle dragons, and 2HKO Trevenant and OHKO Kyurem-B after rocks. Excadrill also has Swords Dance and can tank hits with an Assault Vest, or force EQ users to waste a turn popping an Air Balloon. M-Blastoise and Starmie also have wider coverage, and Blastoise can even scare off Ghosts with Dark Pulse. Donphan also lacks recovery (which most Defog users and Starmie have), suffers from 4MSS, basically needs Earthquake/Rapid Spin/Ice Shard/Stealth Rock, loses to most SR setters, and is walled by Mega Venusaur. Yet it's 38th in usage in last month's statistics. That's higher than Deoxys-S.
Starmie for B-Rank. It has a negligible power loss from Mega Blastoise in exchange for more speed, the ability to hold any item, BoltBeam coverage, decent recovery, and can surprise Mega Venusaur that attempt to wall it with a Psyshock.
Highlight Donphan's placement in E-Rank. Outclassed by Excadrill in the offensive department because the mole can actually beat Mega Pinsir, outspeed and OHKO non-Balloon Heatran and Rotom-W that's uninvested and without a scarf, handle dragons, and 2HKO Trevenant and OHKO Kyurem-B after rocks. Excadrill also has Swords Dance and can tank hits with an Assault Vest, or force EQ users to waste a turn popping an Air Balloon. M-Blastoise and Starmie also have wider coverage, and Blastoise can even scare off Ghosts with Dark Pulse. Donphan also lacks recovery (which most Defog users and Starmie have), suffers from 4MSS, basically needs Earthquake/Rapid Spin/Ice Shard/Stealth Rock, loses to most SR setters, and is walled by Mega Venusaur. Yet it's 38th in usage in last month's statistics. That's higher than Deoxys-S.