4 out of 5 Bjergsens think Syndra could use a mana buff
Granted, he probably went for too much W harass in lane; using that spell much will put you oom very quickly. Still, he spends a good chunk of the first 10 minutes of this video complaining about Syndra's mana, and even misses a solo kill at one point due to not having enough mana for ult.
After the Q damage nerfs, Syndra is a much less oppressive lane bully, and the E stun width buffs also hurt her as well. I'm not asking for a revert on those nerfs, but a little buff to Syndra's mana costs would go a long way towards making her viable again. (Currently Q is 40-80 and W is 60-100. Personally, I would put Q at 45-65 and W at 50-90, but I'm no balance expert so I might be wrong.)