you can certainly run shroud at level 15. i just may be a bit hard to find someone that will let you into their group, especially as a first timer at level 15 on a caster. you will get almost no XP as you are getting severely power-leveled by the level 20s, but its worth doing just to get an early start on your ingredients and shards of power imo.
the biggest problem youll have with being a 15 caster in the shroud is that you dont have wail of the banshee yet. in parts 1 and 2, its usually my most used spell. bring a few major spell pots so you dont run out in the middle of one of the parts. having a good amount of pots may help you to get into a group more easily.
Pre-Part 1: pass out GH to everyone as soon as everyone gets inside. no need for blur as people wont be taking much damage. throw a haste right before you go through the portal. if there is another caster in the group that is a higher level, you may want to see if he can pass out GH as he will most likely have more SP than you.
Part 1: when you first get in, cover the whole map killing the trash with Finger of Death/Wail of the Banshee. then run from portal to portal killing the trash that comes out of it with FoD/WoB. cast haste from time to time when a large group of melee's are at a portal and the buff is burning off. the portals take negative energy damage so throw on an extended death aurora if you like. its not going to do much damage though, and other than that, you wont be doing much damage to the portals.
there is a pattern that most groups follow between all the portals. ususally as a caster, you run ahead of the group to clear all the trash before the group gets there. since its your first time, either follow the group and clear the trash as you go, or request that one melee leave the current portal early and lead you to the next portal to help clear the trash.
after completing part 1, cast GH and blur on everyone. run to the side where the alter is, people will group there, then buff them as they run over there. use up all your SP on buffs before shrining.
Part 2: run to the bottom center of the map. there will be a big purple barrier and it will be where everyone is running to. whatever you do, do not run to the top center of the map, because you will pull all the red names before the trash is killed and everyone will be very unhappy with you. if you end up at the red names, just let them kill you and get rezed later.
cast an extended Disco-Ball infront of the purple barrier. then cast some FoD/WoB for whatever trash is left. after that when the red names are pulled, cast a combination of empowered Polar Ray and/or Cone of Cold. disintegrate works too, but it doesnt do much damage so its kind of a waste of SP. if you run low on SP, go to the sides and run in and out of the healing caves (it will regen health and SP). just make sure you check behind you that you dont have any aggro and arent bringing any red names with you when doing so.
if you get asked to break the crystal, stand at the crystal and throw 2 or 3 empowered and entended firewalls ontop of the purple barrier surrounding it. once all the red names are prepped or they start to die, spam as many firewalls on the crystal as you can. if you cast enough of them, the crystal will break the second the shield comes down (when all the red names are dead).
the red names walk back to the crystal after they are killed. if they get to the crystal before it is broken, they will respawn. this happens when a red name is killed early. if one respawns, call it out to the group so they know to stop killing.
Part 3: no buffs before or during Part 3.
BRING KNOCK! its the only spell you will need here. it will let you open puzzle rooms for solvers, or to solve them yourself. if you dont know how to do your puzzle, call out your location to the group so they can come help. after that, run around opening doors for people (target the levers then knock them) and/or run to the center room and run water. you get a vial of water by clicking on the face over the pool of water. then you run to a room that has been solved, and click on the face on the wall to place the water. only put water in puzzles that have been finished or you will miss out on 2 chests and people wont be happy with you.
never step on the big gold circles on the floors of the hallways. this will set off a trap and blast the person behind you.
this is a solver for the puzzles. practice with it a bit to get the general idea for them. you can use your 'my ddo' tab to access the internet if you arent aware. save this link as a link in your my ddo for quick access:
http://perfectweb.org/ddo/solver/vale_puzzle.html
Part 4: when you get in, run over to the wall on the side. do not aggro the orthons and devils. youll see where everyone is grouping. lay a discoball and cast a haste on the group. when the trash comes WoB/FoD. when Harry comes, cast Waves of Exhaustion and Waves of Fatigue on him. he seems to resist these spells a fair amount, even on my level 20 WIZ. the effectiveness of those spells on Harry have been scaled back alot, so if you cant get them to cast successfully, no biggie. dont waste too much SP on it. throw a fog cloud or cloud kill on Harry to give the group concealment.
then stand back and cast a few Polar Rays, but ration your SP. rehaste the group if needed. if you dont kill Harry in the first round (which you probably wont), Harry will fly away, and another trash mob will come. use WoB/FoD.
when harry comes back, some gnolls will pop-up around the outside. kill them all using FoD/WoB. this is very important because the gnolls will heal Harry. kill these gnolls off as quickly as possible.
more Polar Rays on Harry if needed.
you may be asked to help heal some of the WF melees on this part, so it doesnt hurt to bring a Reconstruct spell or some scrolls. generally this isnt the case, but if you have a badly spec'd/geared WF tank or some questionable healers, it doesn't hurt to have these just to stop any deaths as no one can be rezed on this part.
also bring some healing pots/candy canes for yourself on this part. sometimes healers will only cast mass heals on the center melees and seem to not pay attention to anyone else.
dont buff before part 5.
Part 5: as soon as you get in, get everyone buffed with Greater Heroism. once everyone is buffed, cast Polar Ray and Cone of Cold on the red names until they are dead. someone should be kiting the elemental on the altar. do not attack him the elemental. when everything is dead but the elemental, run back and forth over the corner of one of the pools until you regen your SP.
the group leader will tell you to kill the elemental when all are buffed and both healers have full SP. when the elemental goes down, Harry comes back. cast Waves of Exhaustion/Fatigue and a concealment cloud on him again. then stand back and cast maximized/empowered Polar Rays and Cone of Cold (if you are close enough) at Harry. when you run low on SP, run back and forth over the corner of the pool. sometimes you may be asked to help heal WF melees on this part, but generally not.
at the end, be ready to cast either a Dimension Door or Greater Teleport for anyone that wants to leave before completing the raid. DO NOT click the alter until everyone is out that wants out. its a good way to **** off alot of people and potentially get blacklisted.
sorry for the giant wall o' text, but thats about the jist of the raid. its really not that difficult once you know what youre doing. run it once or twice, and you should have the hang of most of it.