Throwing rocks 1d4 damage, too high?

@ChrisPerkinsDnD party's rogue has grown a fascination with finding rocks of varying quality to throw at enemies heads. 1d4 damage too high?

— Justin Deering (@Inferno_Jack) June 15, 2016

Here's a point of comparison: a sling stone deals 1d4 damage. https://t.co/crljuEUgsW

— (((Chris Perkins))) (@ChrisPerkinsDnD) June 15, 2016