As an owner of an iPad 3 since it was introduced I can assure you that graphics performance is not underpowered, in fact it plays smoother and with higher frame rates than the Nexus 7 tablet recently released.
The iPad 3 came out last Mar'12. The A5X in it had 2 CPUs and 4 GPUs. Samsung non HKMG 45 nm process was used to build it and the die was huge 165 mm sq. Just a few weeks later ( May '12 ) Samsung brought out its own Galaxy using 32 nm HKMG ! The iPad 4 was relaesed Oct '12 with the A6x in it still with 2 CPUs and 4 GPUs but built with 32 nm HKMG ( device shrink factor 2 ) and the die only 124 sq mm ( die shrink factor 1.33 ), so presumably 50 % more transistors, apart from having a more advanced design.
The root cause of the iPad3 being weak in graphics was that Samsung built the Apple A6 with their non HKMG 45 nm process. Even with 2 GPUs the die was huge and dissipated a lot of heat which is why Apple had to use a Heat Sink on top of the SoC. Several months after the iPad 3 Samsung brought out their own Galaxy S3 using their 32 nm HKMG process. A few months later Samsung used their new Fab process for Apple's A6 in iPad 4. This episode exposed Apple's vulnerability from depending on just one Supplier with its own ambitions.
The results from anandtech also shows a similar pattern. The chip is underpowered for the resolution and does not deliver comparable "fps" for the retina resolution vs standard 1024*768 resolution...