The Ryodan's strength is an interesting topic, and I believe that they are very strong.
Kururo was able to survive his fight against Zeno and Silva, and he wasn't even using his full strength, and while they themselves were holding back, being able to survive for so long is a feat in itself.
Nobunaga is a skilled swordsman, and Machi has shown her strength with the threads against the Mafia, not to mention her speed when capturing Gon, while Franklin is both wise and powerful with his nen bullets and large build.
Phinks is very strong, as shown with the arm wrestling matches and his sheer power to literally turn heads and kill in little time. Even one of his most powerful moves was miscalculated, meaning that he's more than capable of killing with greater ease and using less strength than shown.
Feitan, shown to be a top assassin, is quick on his feet, and strong enough to quickly slice people's heads off without a sweat. His special abilities are also extremely powerful and dangerous, as stated by Phinks, who isn't one to compliment anyone.
Uvogin was able to take out an entire squad of Mafia men, take down four of the Shadow beasts, and his fight with Kurapika was a long one, not to mention his bang impact barely taking any of his strength, since he didn't even break a sweat doing so.
Pakunoda's skills, while not regularly for fighting, are very useful, and she knows to to use them properly, and she did hold her own against the Mafia quite well, and Shizuku was able to easily kill many powerful nen users with Blinky with little problem, and Blinky's ability matched with her intelligence were brilliant against the chimera ant.
Shalnark is the only Hunter out of the entire Troupe (excluding Hisoka), proving that he is strong and durable, as it's rare for a hunter to use nen in the exam itself, and his skills, while usually not for fighting, were used well when against the Mafia, while his special ability, with its risks, is sheer power, and should take years to master without killing oneself.
Kalluto is a Zoldyck child, and has shown his skills in torture, so while he isn't as strong as the other members, he's still a force to reckon with. Kortopi has no know fighting skills, but his ability is very useful, and Bonolelov has shown to be a skilled Dancer fighter with his capabilities.
Now, the Troupe does know who's strong and who isn't when it comes to certain enemies, as shown various times. (Machi telling Shalnark to watch the others fight, Kururo telling Nobunaga to protect Shal, Paku and Shiz with his life, etc.) They do have their weaknesses, but I think that they're more than capable of taking care of the ants. They took them on one by one, without any previously known knowledge of who they were dealing with. Besides, they only used their abilities for practice against the ants because, as Phinks said, it was a race. If they had been serious, they would have dealt with them differently.