Well....chameleon skinks will often perform more as a mixed bag unit. Against certain opponents (such as OK) they are brillient, against others (such as Dwarves) not so much.
1) Against a shooty dwarf army I would advice you to simply leave the chamo skinks at home. One of the greatest strengths of Chamo skinks is to march block opponents, and dwarves cannot be march-blocked, and beyond this a gun-line army wont be moving very much anyhow. If you take them, I would agree that you should go after thunderers and the like. However, I would think that the special slot would be best used by another terrie unit in this situation.
2) Against a balanced empire list, chamo skinks fare better. As there is 1 less crewman on artillery crews (one should always assume that a dwarf will take an engineer), and as empire has a lower leadership, you will have a greater chance of inflicting damage through rolling panic. That, and the Empire's lack of effective skirmishers means that you can march-block till the sun goes down when residing in a well-positioned forest.
3) Against Ok, deploy as close as possible, and march block from the first moment. Although Chamo skink poison will actually prove effective for once, you will more likely use that 12" move to get in his rear after his first move. With both of you moving at 6", you can pepper away until he commits a gorger or lone character (at which point the chamo skinks have already paid for themselves)
