Politics are different now and Pakistan doesn't have any restrictions as long as it can pay, this stands for US hardware as well but now without support offset funding. Pakistan can buy Mi-28s if it wanted to but we need to understand the role the helicopters will primarily perform.
Pakistan's cobra's primarily are used for COIN in hot and high areas. T-129 is lighter and to some extent has a cockpit with better visibility than the alternatives. This would result in better high altitude performance. The AH-1Zs have excellent high altitude performance as well.
Mi-28 and WZ-10 are primarily anti armor platforms and are heavier because of more armor.
WZ-10
Mi-28 empty weight
T-129 empty weight
Pretty simple to understand both T-129 and WZ-10 have almost same thrust engines but the weight difference would mean the WZ-10 will have comparably sluggish handling. WZ-10 range is also lower. I personally like the WZ-10 design and nevertheless a better powered WZ-10 is in the works but there is a huge Chinese internal order requirement for it and Pakistan's urgency could be the reason it is not waiting for it.
The Mi-28 is simply overkill and will be more expensive to run, plus has lower service and hover ceiling, so not ideally suited for Pakistan's COIN needs.
TOT is an absolute must for Pakistan because in COIN these helicopters will come across small arms fire and will repeatedly need to be patched up, most often cockpit and crucial areas are armored but rest isn't. If you do some searching up PA has been really busy fixing bullet holes and rotor damages on it's AH-1s.
As per my understanding Turkey has offered Pakistan a work share arrangement as well as TOT. This means PAC Kamra will be making parts and spares of the T-129 for other customers as well. So T-129 apparently a win-win.