Rousseau scares me. The other Miami #15 Jaelan Phillips had a really good year. He was a former #1 overall HS recruit who has battled injuries and finally flashed his ability. If the injuries are behind him, he could be a much better pro. 6'5 and 266 so pretty good size, but he'll need to bulk up to be a 3-4 DE.
What defense do the Giants run? 4-3 or 3-4?
The short answer, a little bit of everything depending on the available personnel for any given game. Patrick Graham really mixes it up with a bunch of different looks, but plays a lot of zone (mostly due to blitzes not getting home) and tries to use his DBs to cover the clear LB shortfall.
If the Giants didn't lose two of their "best" Edge players in Lorenzo Carter and Oshane Ximines, I think they would try to consistently run more 3-4. (Important note: being the best Edge on the Giants is like being the tallest dwarf.)
As it stands now, the Giants strength is along the DL, with Leonard Williams, Dexter Lawrence, Dalvin Tomlinson and BJ Hill, so I think they run more 4-3 than Graham would prefer. But while that frees up MLB Blake Martinez to make plays, the DL tends to get worn down since they cannot substitute and the offense hangs them out to dry for stretches.
When they run a 3-4, outside of RILB Martinez, ROLB/DE Jabaal Sheard (who is really just a complimentary player on a good team) and maybe Carter Coughlin (a 7th round rookie) in LIMITED spots, the rest of the LBs are borderline atrocious to a complete dumpster fire.
Some people like Tae Crowder as a nickel LB, but I am not sure I see it. Graham also tries to work in players like Jabrill Peppers at LB to cover up the shortcomings, with modest success.
The scheming has been relatively effective against mediocre or one-dimensional teams (it really gave fits to the Seahawks and Bucs), but the Giants desperately need to upgrade at Edge and I would really like another LB (Parsons?) that can run sideline to sideline.
For whatever reason they keep trying to get David Mayo reps and he is trash. I think he is one of those players that instills confidence in the coaches, because he knows his assignments in practice, he just can't execute it in a game consistently. But the staff would rather get burned by physical limitations than mental errors by younger players.
The Giants have some players in the secondary, which helps, but they need that CB2. Graham seems to want to have "positionless" football players, which is a great idea in theory, but I think that is a bit of a cop out for players that don't excel at a specific skill/position.
In my opinion, it shouldn't take too much to get to the next level on defense, especially if they are drafting in the top-10, and the Giants should have cash to add a quality free agent or two, probably one player on each side of the ball.
They probably have to decide between either resigning Leonard Williams or Tomlinson, who are both free agents. I would sign Williams, let Tomlinson walk and use the money to add the best Edge or CB they can land in free agency.
Then maybe look to get the other player with their first or second round pick in the draft, unless they go LB as the BPA, bring in a placeholder and wait to fill that third hole or get lucky and uncover a surprise in the middle rounds of the draft.
Overall the defense has been a pleasant surprise, but a talent infusion is needed and resources need to be spread out a bit better.