All other missiles you mentioned have payload of <1ton
Agni V TD-3/MK-3 will be less than 30 tons but it will have payload of 1.5 to 3 tons. The RV will be bigger bcoz it will need more fuel which will reduce the height of other solid engine sections.
i dont see Agni V TD-3 crossing range of 8000 KM for full payload configuration!!
Do remember that composite tech, India is using in Agni V TD-3 is 20+ yr old tech
All modern ICBM are fully composite!!
RT-2PM Topol
All three stages are made of composite materials. During first stage operation the flight control is implemented through four aerodynamic and four jet vanes. Four similar trellised aerodynamic surfaces serve for stabilization. During the second and third stage of flight gas is injected into the diverging part of the nozzle for flight control.
Their specific impulse Isp is better than Indian rocket engine. Russia have 6 decades R&D experience in solid rocket propulsion. IF their engine have 10% better efficiency than Agni engine;then range would change vary by 20+%
Agni V new version will be similar to DF-31 in performance!!