The efficacy of Wards is inversely proportional to the degree of difficulty one plays at, due to the inherent bonuses the opposition gets on higher settings. On Master, in fact, almost any single attack from boss-class casters will shatter even the strongest Ward, which is precisely the sort of situation where you most want the thing to hold. They do still work against Dragons, though, since breath attacks are DoTs rather than single impacts so get continuously blocked over the time period they're active.
There's also the issue of them being rendered largely superfluous if you go for high magic resistance, since then those attacks don't hurt much to begin with, or if you use the Atronach stone and/or perk, in which case you'll be absorbing many such attacks so won't care if you get hit or not.
Actually it's the opposite of what you've suggested, the damage over time spells break wards faster than strong projectile spells. Wards regenerate when they're not hit, so you can take quite a beating from enemy mages projectiles (on master) but as soon as they use sparks, flames or vampiric drain it breaks pretty dam fast.
Wards are brilliant against high level spell casters (obviously the greater ward) at range, even on master. They are extremely useful against one hit shouts such as disarm and unrelenting force (draugr deathlord) or fire/frost breath (dragons, not the continuous shout).
But you are right, they are rather useless if you have a high magic resist or magic absorption. I enjoy using them on my mage characters, who I purposely don't give much magic resist to.