You could wait but the primary reason to do them at 248+ is because of the gap from about 248 to 254 that you lose experience to level difference at both grind spots (Evac and Storage).
Being 248 when you start Ibre Plateau puts you 10 levels above the map suggestion. And you can put each map at an average of 1 level per quest clear/exploration. This will put you at about 252-254 by the time you’re at Steel Heights, which is 253 map suggestion. You shouldn’t have too many problems doing it this way and this is hands down the best time exp/h-wise to get and use these cards.
Granted, I get where you’re coming from, some of these maps are a pain for some classes. Namely the Cronewt Needlers and Cronewt Magicians, and maybe even the Hohen Mages. Yeah I had to use a couple bon fires and a good amount of potions (10-20 per zone) while questing through these zones as an equal-level archer.
Regardless, I still believe this is the best time to do these quests. You may struggle depending on what class you are, especially if you’re solo, but it still should beat the exp/h you’d get in Evac at this point.
I think dvine can help you out, since he’s leeched a lot of people in dina. Once I get ele3 wl on my other character I can help people leech in dp2.