Explosives have 3941 HP in +7, 4960 HP in +10, 7292 HP in +15, 12493 HP in +22. I picked a random log from FH+23 that happens to feature a 3.3k resto druid:
https://www.warcraftlogs.com/reports...-done&source=1
Even if this druid only did a +15, only two of his abilities can one-shot an explosive: Shred (only if it crits) and Ferocious Bite (a spender that is usually used at 5 combo points with 50 energy up). A resto druid has no reliable tools to solo all explosives.
One the other hand, a holy paladin or a monk are great at soloing explosives. And that shows one of the common flaws in the community - everyone will sit around waiting for a resto druid on a week when other healers can handle the affixes better.