Yes, setting aside the level gating, it looks like the conversion from old destiny/fate points to the new system is reasonable and fair.
Yes, this is the part of the revamp that is most complete and positive. Lots of players have asked this to be simplified for years. Definitely makes running a new character up easier. SSG nailed it as far as I can see
Maybe. This is hard to tell for me. The degree to which I'll miss twists of fate is hard to discern yet. They allowed for a lot of flexibility. Currently, you can get 5 twists and that means you could effectively cherry pick from up to 5 other destinies to complement one maxed destiny. The revamp lets you go much deeper into 2 other destinies to complement one maxed destiny - however the "mantles" are mutually exclusive which limits the benefit of going deeper. Maybe this ends up mostly neutral because there's some flexibility loss and some gain. The level gating really affects this too; at 20 I'm certain you'll have many fewer interesting combinations, at 30 you may indeed have more.
No. This is the part that was going to be the toughest design challenge. If there's a commitment to level gating I don't know what else you can do to make level 20 feel as good as it does now on a character with a maxed destiny and some twists of fate. You'd have to have some really good abilities available at 20 and what I see looking at some of the new trees, the lower tier abilities are weak; the first tier of each mantle is weak; the first core is weak. These needed to be buffed quite a bit to counter the level gating.
I don't know why this kind of level gating is such a focus and goal. But it is what it is, SSG wants level gating. What I was hoping is that there'd be enough really cool, and/or powerful, and/or fun new abilities that would offset the shock of hitting level 20 epics with so much of a weaker character. Looking at how epic leveling will be now, and I'm really dejected and unenthusiastic about the entire revamp. Whereas before you could get the entire basket of fun at 20 and use it through 30, now I cant even play with some things in the basket of fun until 30!
It's tough. The only actionable idea I can give is drastically relax the level gating requirements:
Heroic tiers: level 1, 2, 3, 4, 12
So for epic tiers, what is wrong with a similar pace: level 20, 20, 22, 23, 26
Please don't use the excuse of a level increase to lock good abilities to 29/30; who knows how far off that is.