What you are suggesting is making the suggested newer Expert dungeons punishingly difficult right out of the gate. Again - straight to one end of an extreme, never trying to meet in the middle. You can't do that right out of the gate, because all it does is give casuals and casual-midcore level players only the options of either wiping through it and deciding never to run these new types of Expert dungeons again, or opting to get carried through it just for the rewards, and hopefully learning the patterns that will get them through. That's a Leeroy Jenkins situation. You're taking the suggestions that I've been making and saying that they need to be hard right out of the gate.
I'm suggesting putting a gradual difficulty curve, spread out through multiple Expert dungeons that increase in difficulty as you approach the last of whatever set of Expert dungeons you will have, with watered-down-to-slightly-less-punishing mechanics from whatever the Ex/Savage tier placed into it. And again, Shinryu is the absolute bar for difficulty. Nothing dungeon-wise should surpass what that fight through at players who were, at the most, ilvl310 in that time-frame. The very last Expert dungeon in 5.0? Sure, make it about Shinryu-level hard. But the preceding Expert dungeons should gradually build towards this point. The devs are capable of it.
I don't understand why you are not able to see a middle ground between the current dungeons and Savage/Ex (no, Shinryu is not a middle ground...he's just the epitome of a storyline and an appropriately leveled boss fight...the dungeons preceding him are another story). Why must it be 'either this or that' with you? That's a serious question. Why? I really want to know the answer to this. Do you deal solely in absolutes? Because in the past, you've suggested something similar about raiders as well, that raiders in general find practically anything dungeon-wise easy.