Alexander in general is 100% optional. You can completely avoid the raids and still be able to keep current with the requirements for the main story and other extra content.

Unless you're hellbent on getting your main job to BiS, you simply don't need to ever enter the raids.

There are multible paths to get your gear to the needed iLVL to enter content. New crafted sets are about to drop, the more recent dungeons and 24 mans, and we're getting new tomestone gear, so you don't need to fear the game past 60.

Weapon wise, you can try the EX raids, Palace of the Dead, or the Anima quests, so you have options there, too.