Keep maxing E second bro. W gives you slightly more damage, but you're not using W for damage really. W slows them setting up for combos. Maxing E reduces it's CD and the transcendent bonus makes the hitbox 50% wider (that's huge). E is really your only defense if you get jumped on or need to self peel, so you need the CD low, and the 50% width bonus makes it devastating in teamfights. The transcendent bonus for W is that she grabs an additional orb, but according to the wiki "Syndra will throw the assortment of units in a way that increases Force of Will's area of effect, but it does not cause the ability to deal increased damage." Which is good for teamfights, but which is better - landing a W on a group of enemies, or landing an E? E also has similar base damage, W scales better yeah but the base damages are fairly close. Think about Lulu, a lot of people max her E second when they shouldn't, should max W second, because the CC offered from maxing it first is much stronger overall (at max rank whimsy lasts 2.5 seconds, compare that to Morg q's 3 seconds, and whimsy silences you! And it's targeted! Point and click YOU DO NOTHING for 2.5 seconds, people should play her more lol) Damage helps you, but CC helps the whole team.
When I play Syndra, I don't typically use W to harass. The only time I'll do this is if I see a one-shot minion I can grab up with it and fling at the enemy, which means I'm really just using it to last hit when I think I'll miss it otherwise. Mostly just try to land Q repeatedly, and if they stand behind an orb, hit them with the E and then maybe combo them. W does eat mana like crazy.
Scatter the weak only costs 50 mana at all ranks. It's cheaper than all your spells except Rank 1 Q, which is 40 mana. Seriously, that is soooo cheap.
Overall this just means is blatantly better to Max R>Q>E>W
Let the bad Syndra's max their W, we know better lol. Scatter the Weak is just a better spell than Force of Will. MUCH lower mana cost, slightly reduced damage in exchange for CC and KILL POTENTIAL. Nobody is scared of a W, but the enemy ADC will be afraid to get anywhere near you if he knows you can stun him a whole screen away. That kind of respect should tell you everything. Stunning a backline is OP.
I haven't tried this myself but it could be worth it (at least in laning phase) to bypass W entirely and just max Q and E (to attempt to make the most out of her transcendent passive). It was a better idea back when the transcendent bonus for Q increased the damage, her passive is kind of ass now. I dunno why they even changed it.