IIRC, in D2:DC there is only some random loot in the chest that appears briefly after the lever and timed platform jumps. It is potentially nice loot, but not worth worrying about if you cann't get the timing and drop down fast enough to open it.
I didn't find the necromancer fight too hard as a ranger. I needed to keep my distance from the demon and necromancer, and not stand still very long, but with my creature in the thick of battle I whittled down the memory eaters and summons relatively easily, then went after the bosses.
Way of the Ranger would have helped (increasing the damage of normal attacks and the effective range of Splitting Arrows), but I didn't know it at the time (don't usually bother with temporary boost skills, but I eventually maxed that one).
