Don't worry, Sastasha is very much a 'training dungeon' as most of what happens in there is easily dealt with and is a basic introduction to dungeons in general. The puzzles are simple (a note near the start informs the player what coloured coral to open the hidden door at the courel fight, pulls single targets from groups of pirates, ignore the groups of pirates in the pub brawling etc). Really, I've done Sastasha with only three people in the party after one person DC'd near the start and never came back (I was CNJ healing at the time). Even the boss fight at the end is pretty simple to deal with. Just make sure you click on the bubbles that form to stop more enemies coming so you can focus on the boss.

Sastsha is very intimidating to a new player though, but like I said, keep a cool head, and you'll easily triumph.