I did include icmp echo directly to each hop as a comparison.
Right, but from what you posted you didn't send 1500-byte packets. My reaction was the same as Lincoln's -- it smells like a Path MTU problem. To repeat -- ping and traceroute RTT from intermediate nodes is at best advisory, especially on timing.
I should add -- DSL lines often use PPPoE, which in turn cuts the effective MTU available for user packets. If the PMTUD ICMP packets don't get through -- and they often don't, because of misconfigured firewalls -- you're likely to see problems like this.
Of course, and thats why I have cut down ip mtu and tcp adjust mss and all the rest. Not making much of a difference. Furthermore, ipsec performance with normal sized icmp pings is what I was referring to, and those are nowwhere near full-sized.