Beyond the removal of stupid shit like OMA toobing, the lack of a Harrier will have a significant impact on the amount of bullshit chains that average players can pull off.
Going Harrier into whatever was really, really easy, and that crutch is no longer there.
Also look at the assault killstreak distribution - there's a gap between pred at 5 and the heavy hitters at 9 - and Pave Low has been moved to 12 (its power getting the respect it deserves), and the only other offensive streaks between those numbers are Airstrike at 6 and Attack Heli at 7.
Osprey Gunner is at 17. Yeah you can get there from Reaper with a good spree, but Pred-Reaper-Osprey is a lot less shitty than Pred-Harrier-Chopper Gunner. 5-7-11 was too damn good (as was 5-7-9, due to pave low).
The addition of pointstreaks means that the 10-15 streaks are easier, but even so, it's still not as easy as going 4-5 kills, drop pred, drop harrier, drop cgunner/pave low/ac130 immediately.
Instead you get Pred... Attack Chopper/Airstrike? Or Pred, work your way to 9 for AH-6 or Reaper. Either way, it's far, far slower and harder than just mashing right on the dpad and suddenly piloting a lethal killstreak.