NO it is NOT NORMAL.
Dripping from T&P Relief Valve will cause corrosion on t-stat terminals/spade connectors or on gas valve solenoid depending on which Brand of RV water heater.
That will cause 'other' issues/problems.
'Weeping' from water heater T&P Relief Valve is an indication that the 'air pocket' has been lost.
Water SWELLS when heated.
By design an 'air pocket' at top of WH TANK allows for the expansion of heated water w/o a substantial increase in pressure.
Water can not be compressed so w/o an air pocket the pressure will increase and cause the T&P Relief Valve to weep due to RV plumbing being a 'closed loop system'
Air pocket is normally established during initial filling. Can get absorbed into water over time
To re-establish air pocket
Turn off water source supply
Open closest faucet hot side to relieve pressure....leave open
Open T&P Relief Valve via lever...caution water hot.
Let it SNAP closed when water stops running out
Close faucet
Turn on water source supply