Good sources of Block are the Ascendancy Skill, Bone Offering, as well as other passive abilities and equipment. An poe currency
important caveat of Block is that it does not mitigate harm over time or other secondary damaging effects.
A good method to compensate for Block's inability to mitigate damage over time is conducting the Keystone, Mind over Matter. MoM is popular in a lot of builds in 3.3, for good reason. MoM takes 30 percent of incoming harm from any source, and redirects it to the mana pool, instead. In other words, 30% of the life you would have lost, becomes lost mana. As long as it is possible to keep your mana pool topped off with sufficient regeneration, then you will enhance your endurance considerably.
The Arc Witch isn't a passive build. You have to be always on the move, and in your toes. You also have to be able to keep tabs on the timing of a whole lot of different skills, buffs, and other items. If you are not on top of your cooldowns, you will not be getting the most out of the construct's rotation.
When you've your rotation down, the Arc Witch is very easy to play. Simply approach a bunch of trash mobs, spam Arc till they're dead, then move into another bunch, and rinse and repeat. It is recommended to use poe review
Flame Dash on event to acquire an Arcane Surge proc, and use Orb of Storms in the middle of a group of mobs to receive your Elemental Overload proc.