>>30934035get a form of Fire move to use under the sun*
And to add to the list of abilities, Hydration is actually pretty fucking amazing since there are good water tanks that get it (Vaporeon, Manaphy, Lapras, Whiscash)
The list of defensive pokemon that learn Leaf Guard? A fucking hugeass list that comprises Tangrowth and Chikorita that as mentioned before, can't even properly function as a defensive mon under the sun because they get an easily exploited weakness under it
And while Solar Power is legit good, ONCE AGAIN, the extensive list of mons that get it is comprised of Charizard, Sunflora and Tropius. Two of those are slow mofos that would actually prefer Clorophyll (and even then it gets to the point that Tropius would rather run fucking Harvest and try its luck at regenerating Sitrus Berries) and the other one was Charizard
So out of an extensive lists of abilities that "benefit" from Sun, the only "good" users are Charizard, Venusaur and?
Gamefreak is biased and hard towards water types. Water types are the most numerous in the games, Water types get Ice beam to cover their weakness against Grass types and plenty of good abilities and abusers under the rain
Meanwhile, what does Fire/Sun get? Extra weakness to rocks, 1 ((ONE)) good Sun abuser, and their coverage against Water types needs two turns to charge and actually gets WEAKER under Rain.
Mind you, that everything that I have posted doesn't cover post-gen 5 as Gamefreak actually made a sensible change for once and nerfed the weathers, but even with the nerfed weathers the underlying issues stay. Gamefreak knows shit about balance. An added weakness to Poison or another type would help to make water less unbalanced.