Wait, turtle shell, are you referring to Omega shell? I never recall those shield been good in the first place. If you are referring to the tortodrone shell then IDK what you are talking about as those shield, barring the grand tortoise are all pretty good if you can look past the MSD: low.

1. The game is still in sort of a limbo state (AKA maintenance mode), maybe 100~200 players in a state of flux.

2. The forum community here is almost dead, not sure about the in game community since I was never interested in socializing in Haven. More of a forum goer. But I assume knights are still showing off their LUDICROUSLY ECKPENSIVE 200MILL WING+AURA COMBO OMGWTFBBQ cosmetic set to the noobs passing by.

3. Depends, what rank are you on, it is hard to guess when you can reach a soft cap, I am going to assume here soft cap means：

-You acquired at least 1 weapon for each damage type, no normal damage weapons needed, they still suck as always.
-You acquired at least 1 shield for each damage type, again, normal shield is not necessary.
-You acquired at least 3 sets of armor (helmet + armor) for each damage type.
-No trinkets are needed, I reached vanguard without it.
-Not all of your gears will need to be fully heated.

If you start from the beginning then I would put 4~5 months of consistent grinding for maybe 5~6 hours a day, so long as you are willing to put up with farming the same place over and over again.

4. Depends on what you mean by PTW, can you buy all the weapons in the game with your wallet? Yes! Can you heat them to full with your wallet? Yes! But I would say no one in SK has ever fully whaled themselves to the top, it would be a colossal waste of money the likes would make gacha games look reasonable.