Better bats than Kallis since 1990:
Tendulkar, Lara, Ponting, Waugh, Dravid, Inzi, Sanga and maybe Flower
I think you'd struggle beyond those guys and beyond the first 3 Kallis probably could be said to be better than the others.
Better bowlers than Pollock since 1990:
Warne, Murali, McGrath, Waqar, Wasim, Ambrose, Donald and I'd say thats it.
So both are roughly in the top 8 of their specialist field in their era and easily provide more with the ball (Kallis) / bat (Pollock) than their counterparts.
Bits and pieces cricketers for sure. Really you could argue Kallis is in the top 50 (or 30 if you are more adventerous than me) of bowlers in his era, how isn't that an essential player? He is at the top in his specialist field, the difference is so negilible beyond the best 3 and the rest of the top 10 batsman.
The same is true of Pollock albeit to a lesser extent.