early on I think Roc is one of the only "smash" Blades. Some of the tank blades can Launch, and the break / topple is normally handled by your standard crew. Make sure you keep tabs on your "4th" weapon ability, I didn't put in Rolling Smash on Rex until the very end and it seemed to really help with Agro. Some of those 4th abilities that you can swap in can help with the "driver combo" chain a bit more too.
Ditto on what Zerkon said, Zenobia is crazy good for Tyrant Killing and Raw Damage. I found that Nim was also extremely good on a healer because she basically splash heals about 50% of the damage she does once you get her maxed up. It gets kinda mashed up because you basically want to run with 6-8 elements, the proper class roles / combo's of blade type, weapons that are skilled up that you like and then if you can squeeze it in....abilities that can get you a driver combo. I think I only ever got about 70 full driver combo's (one of the blades has an unlock for doing 250 full driver combo's). I never spent the overdrives to really try and line it all up, so the full driver combo (break > topple > launch > smash) was never something I did much of. If it lines up that the characters and blades you use can pull it off regularly then great, but I don't think its a deal breaker to not be able to regularly perform them.