Use mindgames is what I would advise; be unpredictable. An arrogant, over-confident player opponent that think you're just projectile spamming won't read you too much. The more avid-experienced players that can see a grab coming when they're blocking an Arcthunder/fire are indeed problematic - what also doesn't help the matter since Robin is so damn slow in approach.
Against character fighters that demand you to react quicker if you want to keep pressure off you and onto them such as Sonic, Thunder and Elthunder is quick enough for them to think quickly or risk giving you space. If they manage to shield against that and attempt to rush again - use thunder then quickly rush in with a dash attack/grab(experimental, I don't usually use Thunder this way but rather to keep the distance and pray they roll away or towards me for a deadly smash attack). If that doesn't work, there is always your wind/fire jab or down A.
They're Pshielding your faster projectiles now? Then the guy pretty much has you figured out on the projectiles department which puts Robin in a pretty serious disadvantage. I would end up using books as a new form of projectile, and books are something that should not be ignored.
