Absolutely no. Not even close.
On price alone, it's a poor deal. Brooks isn't worth 700k. He's having a good year (for his standards) and we're still basically last, despite having a forward pack of internationals and origin players. Sure our backs aren't great, but Brooks just isn't that good a player. Given there is a lack of proven first grade halves on the market, Brooks' market value is probably in the 500-550k range (which is what we correctly offered). He won't win you a game on his own, but can be a complementary piece in a winning side.
The length of the deal is also bad. 2 years or 2 years + option is the most he should be getting. 4 years is what you're locking down a rep level player for, or a youngster who you think is going grow throughout the term of the deal so they're on unders come years 3 and 4. Brooks is going to be 29 starting that deal, 33 finishing it. He's absolutely not a rep level player, nor is he someone who is going to improve throughout the deal. Given he's lost a step of pace (which is his biggest attacking asset) and is now starting to have injuries creep in (calf, hamstring), it's much more likely he regresses throughout the term of the deal.
Ignoring everything about his past at the club, the fact he needs a change of scenery etc, we made what I think was a pretty reasonable offer based on his ability, experience and future projection. 2 years at 550k a year. The contract he's received from Manly is absurd and unless he immediately hits the ground running and shows far more than he has here, it will be a deal that works out very poorly for them.