Is the gen. corp. team at Dentons-LL any good? How is the work-culture and pay scale?

Highly depends on the partner you join. It's a typical lala firm, however its trying to get professional. Pay is really really bad. Having said that, it's a good starting point.

It takes crappy tier-3 nlu students who have barely managed to pass each smemester. The pay is 3rd class

Then how come link legal associates are always poached? Do they make crappy law students into poachable associates?

Teams are at par with Tier 2 firms and there are some teams which punch above their weight. While work culture depends on the Partner, it's a lala driven firm with one family at the helm with Partners having little to no say in overall management of the firm, increments, etc.