In D2:ED I leveled in the fjords before going to Sentinel Island, to get the most effect from mindreading the island character, and barely even noticed the bandit trying to heal. Finishing Maxos temple almost brought me to level 16, and I got to 18 in the fjords, so at the start of the island I was level 19, and got another level or two by the time I cleared everything else and started on the battle tower.
BTW, there is a hidden cave on the island...
under the formerly windy peninsula with the grave stone; jump into the water to either side of the grave to get to it.
