Chewie is pretty rare to see at higher levels. I'm only halfway through 54 and his low dps makes him a liability so you just don't see him. I dropped him as soon as I got the droid pack a week after I started.
I see a Chewie and I pack Windu and Ventress and it takes care of his taunt, he's an especially good opponent in GW since I leave him for last and just poke at him while I heal up toons and run through cool downs.
I have HK and swap him with Oppress for 5th slot in PvP depending on the opposition. HK is great vs Jedi teams. They're both tanky without carrying the official designation.
I bought the droid pack and got Lobot on one of the few Chromium packs I bought when I first started so my plan is eventually to create a droid team headed by Lobot and maybe add Poggle in the 5th spot (not impressed with IG-100 Magnaguard so far but I don't own him, maybe he gets better maxxed out?).
Edit: HK is also easy to farm in Arena shipments and that alone makes him a better choice IMHO.