I think this small buff would make him little bit more interesting in certain scenarios.
I definitely agree that Kong is under-powered and needs some help, but don’t think this would be the best solution. Since he already provides defense against ice, it would be awkward to give him a different color specific niche. I would rather have him give all allies an attack buff, since that fits with his title - lord of the jungle - and is a common fire hero ability.
It is common red hero ability (but also Kiril), which means that he would override effect of others or vice versa and pairing would become difficult. DoTs are another example. Critical chance (him and nearby allies) is another viable option that would interfere only with Ares.