Ripperdactyls have stood up to the test of time. Especially when inside of the Shadowstrike Starhost. They probably need rend -1 on their bites or feet to continue in relevancy in the era of Bonereapers and Fyreslayers though. They are no Morsar Guard as far as cav are concerned though.
Ripperdactyls are also extremely squishy compared to other hammers. Which makes them far too reliant on the shadowstrike host's ability to dump them on top of an enemy without getting shot to bits. It also means they nearly always get annihilated immeadiatly after landing if there are any survivors.
Also, they're too dependent on their toad.
They're among the worst units statwise in the catagory "elite 3 models units". Only really outperforming screamers of tzeentch (which are currently terrible) & flamers of tzeentch (which are artillery). But all the other 3 model units serving a similar purpose as a (glass)hammer have vastly better stats. Nearly always boasting more wounds, a better save (or at least an additional alternative form of protection like a ward-save or healing), more attacks without needing a toad, often having rend or mortal wounds (or both), and occasionally bringing some ranged attacks for good measure.
Basicly they rely on the toad & the shadowstrikes ability to guarantee 1 good round of combat in a prepared position and that's it. You can't use them like you would a normal hammer and just smash them into a vulnerable part of your opponents line, wherever & whenever that may be.
plus, they're our only option that even resembles a hammer, without immeadiatly needing to rely on behemoths. If nothing else we need some alternative options, terradons, knights, kroxigor, razordons, at least one of those should be useable as a hammer as well.