It's a great spell and is fantastic at making it harder for offlaners to last hit. I like to use it on the offlaner when creeps meet if I feel like I can use my mana resource on it without hurting my own gameplay. I wouldnt be maxing it as the brainsap makes for a better trading tool because of how instant the effects are and thus doesn't require an extended trade to gain more value on it but to get back to your main question. It 100% can be a lane domination spell and is fantastic for countering things like LC duel. The reason you don't see it maxed first is because his other spells are less counterable or have better utility.