DLC average SL

I'm sure there were already plenty of topics on this subjects, sorry if that's the case!
I'm just wondering what was the average soul level required to survive in artoria. I'm SL 150, so I don't think i'm near this average level, it's just in order to see which difficulty the DLC is. (am I overleveled to enjoy it btw?).
Another question, concerning the missable trophies (knowing DS, im sure there'll be plenty in this DLC), have we got to finish the game another time to do the dlc again? (in case we missed something or killed a NPC in artorias) I'm in NG+++ I think and I don't know if one year later i'm motivated to rush 4K, ToTG and O&S again..
Thanks

I didn't understand the questions correctly but I may manage to answer one.
I believe you are aboe average in level in the DLC areas its just a matte of your skill. I am lvl 50 and am about to take on artorias.

I don't think you are overleveled because I have a levl 160 who I am struggling because I never played STR focus toons and I am really having a hard time. But you are doing fine.

Depends are you focusing on PVE or PVP. For PVE doesn't really matter since NG(?) defines how hard would it be. Not to mention unknown enemies and tactics.
Regarding PVP however there is arena and certain brackets. There SL means something because at your SL you will fight in 101-200 bracket.
Lot's of ppl where preparing their chars for certain brackets and they were usually aiming for lvl 50 or 100. 200 bracket could be boring since there is little variety...

Anyway you can stick to your SL and give it a go or start the new one and rush three bosses to get access to a new content as NG.

actually now i'm wondering if it's not better to start a new character. Anyway I got 24 hours to make my mind! can't wait it's like a mini dark souls 2

If it helps, I will go first with my SL120 (NG++) to check it out and then with my SL100 Arena build just for PVP.

Have fun!