We had to sign players and we had to pay overs to do it. There's no 'dumb decisions'. The people who signed those players knew what they were worth (less than they were asking) and they knew the consequences of signing nobody (which was the only alternative to paying overs for players).
We needed new players, we needed to spend most of the cap, and the only way to do both was to pay overs. Hell, we even needed to pay overs to retain players (including, I'm sure, Jarryd Hayne).
Smith has already ben paid his overs when his club was cheating the salary cap. And like Darren Lockyer at the end of his career he has certainly accepted less to stay at Melbourne. Probably also been offered a job with the club post-footy.
And everyone knows the Roosters players are on unders, at least as far as the cap is concerned:
http://www.dailytelegraph.com.au/sport/nrl/phil-rothfield-sydney-roosters-squeeze-8-million-worth-of-talent-into-6-million-nrl-salary-cap/story-fni3fh9n-1227050745642
Just because Hayne is better than other overpaid players on our roster doesn't mean he isn't also on overs. In fact I dare say he is on more. If Hopoate is on 20% (hypothetically) more than he's worth then Hayne is probably also on 20% more than he's worth, and 20% of Hayne's value is a lot more than 20% of Hopoate's.
If you disagree with 20% then substitute whatever value you prefer. But do it for both players and the outcome is the same.