Tbh, why don't they just accept the new roles being given to these classes? It's what makes PvP interesting imo and it breaks the 'traditional' flow you see in PvE.
Healers be your forward shields. Tanks are interceptors, like knights in a chess game and provides oppurtunities for assisting jobs such as drg and monks to make some damage. Tanks and melee dps are still not obsolete, and in capable hands they can make a healer that attempts to be 'forward' walk right into a trap.
Yes.. SCH is hardy. With 5k hp their adlo+lustrate combo (I believe from seeing why they're normally survivable) they're able to take on people by themselves. But if your up against a 'tanky' SCH, chances are their heals aren't great either and you have tools against this:
Storm's eye/Miasma: reduces heal potential, forcing them to relly more on lustrate.
Full swing: 3rd combo attacks from anyone basically does half more than what adlo can shield, and making most melee attacks basically take off adlo right away.
One-ilm punch/Glory slash: Can remove adlo/equanimity/stoneskin/protect anytime a sch does not have adlo, he is succeptable to damage from another dps.
Sumersault: Slower adlo cast, can also be used on pets as well, an unattentive SCH won't notice why he's not getting healed as much if he's being focused.
Debuffs from brds/smns: hides full swing/storm's eye/Sumersault, forcing them to use purify. Can kill through attunement if enough is stacked and Eos/Selene gets focused.
PLD stunlock: Can't believe I forgot this... and this is something you can learn from doing leviathan... geez. Sure stuns are reduced in pvp but 7 seconds total=two GCD attacks and an instant(and another instant from the PLD itself).
Also tanky schs tend to have some sort of god complex and tend to not keep their peers alive. You can always bait DPS away from flags so that you relieve more pressure from your melees. If their balancing this for the sake of 1vs1 encounters, they might as well start implementing a dueling arena that people wanted...