In duels where my opponent heals in any other way except charge to andariel and meditation, I most of the time do not even bother with them. If they use a little harder character class, such as a sorc or a windy, I usually go by their rules, (go fetch 16 juvs from my gf wolf) heal and beat them up bad. However this rarely happens. But that's just the way dueling on Europe is.
However, I have met some more stupid healer people too. One was a paladin, he charged to some random cave right after I had almost killed him. I then said something like "Lol, run", and all he said was numbers in a short time (1,2,3,4,5..), and when it hit 10, he said "Lol 10-0'ed ez, you suck".
Now that was a real killer.
Then there was this friend of mine, who used 1600*1200 mod on all of his characters, giving him a huge field of vision. Beat his Windy and his Blizzard sorc and all he could say "non-block chars<BvC". I doubt he would've been dumb enough to make a non-block windy. The only character of his that I never bothered to duel with was his boner, as the way he dueled with it was the classical walls + im + spam funny words and spirits.
Then there's the occasional BM hammerdin. Have met a few of those too. One, the most common would be NK_YOU, a quite BMish hammerdin. In some games, he used to carry a gmerc. Heck, the only time I dueled him 1v1, it was like this:
*duel begins*
*I get hit to half life*
*paladin gets to belove half life*
*paladin goes off to kill a random in the pub game*
*paladin comes back with full life*
This went on for a few times until I got bored of it. Once I even dueled him and his friend 2v2. That was quite hilarious, as there rarely was a time when both of the teams would be dead or even half dead. BM 2v2, BvC+Hammerdin vs. 2 Hammerdins. Well, of course NK_YOU didn't even play that much, he was just making an invisible field of hammers somewhere around the town exit. At times he and his teammate were trying to corner me and my teammate. A few times it actually worked too.
About the "sinking to their level"-thing. I do not see what the heck is with it. It's not like it's a gang of people who rape women in the street or something. But yet, overall I've beaten more healers playing GM than BM.