This issue clones
MC-154901, since it was resolved due to lack of response for nearly two years.
In 1.10.2 and before, skeletons who were set on fire would have a 50% chance to shoot flaming arrows if the regional difficulty was 3.00 or higher. This no longer occurs, which is presumed to be an effect of the splitting of wither skeletons from regular skeletons in 16w32a, which is the first version in which this feature stopped working.
- Spawn in regular skeletons. Make sure they do not have enchanted bows.
- Set your difficulty to hard and set your day count to like 1000 or something. Make sure it is at least 3.00 difficulty.
- Let it shoot you (in survival mode) when it is on fire
→ Notice that they do not shoot flaming arrows ever