Oh I was also wearing armadyl armor with 135 magic def using ranged attacks and the guthix wizard attacked me with magic... I didn't pray against anything as he kept on splashing..... Weird clue altogether I guess....
I hope this works. Btw I seriously got this location twice in a row. I came here, killed a guthix wizard, dug up an elite casket, and got another compass location in this exact location. Now I'm currently working on a celtic puzzle thingy but what are the odds of that?!