Tales can come in on Ice hits aimed at your Grass mons, the odd special Grass move as well as other weaker special attacks when you invest in bulk reasonably, even including weak Fire hits, as well as WoW and setup (as can any other mon). Her switchins are somewhat limited but are by no means unbelievably sparse, and with a ChestoRest set you can come in on less than optimal moves and heal off the damage or status later. When against other weather users you should always have a different switch that can take out the inducer anyway, so that's somewhat of a moot point.
This is without mentioning that when you take into account the difficulty she can have in coming in, you can adapt your team to help that by using slow Volt Change or U-Turners, letting her come in for free in certain threats. I suppose this certainly makes Sun one of the harder weathers to play with (Hail maybe aside) but I wouldn't say it damages its usefulness.