My experience with two different 180's differs from yours. 115 KTAS is kind of on the slow side for an Archer (even considering none of that fancy pants stuff).
I've flown a lot more than two Archers - And I've only seen one that was noticeably faster than 115.
Averaging 100 KTs over a 411 mile trip would not be a no-wind situation. (btw - that's what I would use for my cherokee 140 before upgrading to 160hp)
I fly lots of long trips in the 182, which trues at about 133. Average groundspeed in the GPS is 119. Your average speed is a lot slower than you think.
Just for the heck of it, I threw together a spreadsheet to figure out how close my estimates were. Since there's 48 gallons of usable fuel and I like to keep a 1-hour cruise reserve, that leaves 38 gallons of flight-planning fuel. Figuring a cruise altitude of 5000 AGL and a 500-fpm climb and descent with the climb at 90 knots and the descent at 125 (the extra 10 knots is about all I pick up keeping cruise power in for a 500fpm descent) plus a total of 6 minutes of maneuvering time for turning on course after takeoff and maneuvering to land.
The above calculations mean the trip takes us 3:42, for an average speed of 111 knots but we're gonna burn 37.6 gallons of our 38 gallons of planning fuel. A mere 2-knot headwind puts us into the 1-hour reserve, a 9-knot headwind puts us into the legal IFR/night minimum 45-minute reserve, a 15-knot headwind puts us right at the Day VFR legal minimum 1/2 hour reserve, and a 25-knot headwind means we'll be landing with dry tanks, assuming we can taxi to the runway at the departure on only 0.4 gallons of fuel.
So, I stand by my assertion that any headwind means a fuel stop. You want to push it to legal minimums or farther, you go right ahead, but you're going to need a fuel stop about half the time too.
Don't forget that you can keep some power in on the decent and get better than cruise speed and lower fuel burn.
I generally keep cruise power on for the descent, only reducing it if I'm in the yellow arc and it's bumpy. I generally get about an extra 10 knots, and that's at the same fuel burn (higher, if you're coming down from up high and need to richen the mixture).
Of course, the Archer is slower than most of the other aircraft you discussed, and the potential for a fuel stop should always be considered. But to claim that the Archer will always need a fuel stop for 411 miles into the wind is simply overkill.
I don't consider planning for an hour reserve, especially on a long trip, "overkill." I fly a lot of IFR and night VFR (comes with the territory when you're using the plane for transportation, as the OP will be) where the legal minimum reserve is 45 minutes anyway, and if the weather requires an alternate I may well need over an hour's reserve just to stay legal.
Considering the OP is also talking about moving on and doing IFR flying in this bird, the necessity for a fuel stop on a gray day means even MORE time, since he'll have to shoot TWO approaches - I plan on 15 minutes per approach, by the time you get vectored around and/or fly a full procedure. So, adding in the climb/descent time for the 2nd leg, the extra approach, and the fuel stop itself means about 1:20 extra because the plane doesn't have the range.
Don't get me wrong - The Archer is a great plane and I think the OP could do pretty well with it. It's just not the ideal platform for the longer trips. (Says the guy who might be taking one to Florida in a couple of weeks.)