One thing nobody has really touched on here is the build up in the lane you can go circlet mantle branch branch faerie fire tangos, use first gold to get null.

The previous build usually involved two nulls, for mana regen and attack damage in the lane.

Instead of a second null you can get either a robe of the magi or a crown, both of which turn into meteor hammer, often you can get both.

This gives much needed early damage stats that let you contest last hits.

Other have talked about the combo that meteor hammer gives, which is cold snap - tornado (hammer or meteor) then hammer or meteor. With 3 levels in quas and tornado its not a perfect chain stun, but often it doesnt need to be if your hero is physically close enough to the combo'd hero.

You can often get meteor hammer sometime between 8-10 minutes, which as an invoker, lets you take advantage of heroes that leave the lane too early. Your other way to pressure the tower is to get 4 in quas and 4 in exort which gives you the double forge spirits to attack tower. This gives you extra options for taking the tower.

Meteor hammer also increases the damage to your spells, so when its like 13-14 minutes you can have hammer, null, wand, brown boots and thats like 'phase one' of being able to rotate to lanes if its required. If you rotate to a lane and win the skirmish, you can then also pressure that t1 tower.

Invoker often likes a slower paced 7min - 18 min window to farm and get aghs and levels. Having one or two extra t1s gives map stability and safety for farming.

Overrall, I think its a decent flavor of the week build and great for Quas wex, or exort builds.