LOL linken. Ok buddy, thats exactly the kind of servers we're NOT taking into considerations here (or else I'm in the wrong place).
We're not talking about +50 weapons and other things like that here.
And probably if the Duelist had +50 duels and tattoo of power like you too he would of won.
But anyway...back to regular, retail like discussions.

PaaGRIO, any selfbuff is considered good magic my friend. If you do Lionheart, Battle Roar, War Cry, Duelist Spirit or even Sonic Focus, they all are considered good magic as in the SA's description and will give you the BtB SA. You can test this yourself. Get a staff with BtB SA and do sonic focus and in a couple of tries you will have BtB.

So that is an option.

I'm not talking about servers with x100.000 rates and weapons that can be enchanted up to +900. And if you're still playing c4 you're two chronicles behind my friend.I could just as well make my own server and make dwarves invincible with custom skills and come here and tell you guys dwarves own every possible class and what combinations to use.But I'm not doing that, I'm talking from the perspective of a retail player.And on retail, in this day and age, a Duelist will own a Titan just as well as a Titan can own him.

Sometimes the Duelist wins, sometimes the Titan will. It depends who uses his skills better and which one gets luckier in crits too.
A glad has the advantage of charging his sonics and nuking so he doesn't have to be near the Titan. But that would give the Titan time to use Guts and Zealot or Frenzy and Zealot. So most Duelist approach the melee playstyle. Get up close, use your sonics in a combo and instill major damage. Some people will say, yes but if the Titan uses a bow he will have range combat abilities too. True, but compare the damage of a titan with 2-handed sword and the damage done with a bow (2h > bow) since last I checked Titan had no bow masteries at all.

Someone said previously that the Duelist is a hero and he used hero skills (Miracle I think was invoked) but surprise, suprise, this is a Olympiad match and you can't make use of Heroic skills (maybe on certain crap private servers you can) so we rule that out of the question.

And something else you have not taken into consideration so far that I see of, in Olympiad you can only make use of self-buffs (no pots, scrolls, etc) BUT there are weapons whose SAs will give you certain buffs such as Bless the Body, effect 5 / Focus, effect 3 / Mental Shield, effect 4 and if the Duelist had, say Focus and Bless the Body then he could of whitstand the Titan's damage and outdo himself by killing the Titan. Moreso, a Duelist has Battle Roar which also restores a certain ammount of HP aside to increasing your maximum HP. So, if you had Bless the Body 5 and use Battle Roar during the fight to restore your HP, you have all the more chances of winning. Yes, the Titan has Battle Roar too but if he used it before the match to increase his Max HP, he will not have it ready in time to heal him during the match.

All in one, a Duelist CAN kill a Titan, just as well as a Titan can kill a Duelist. It's all about knowledge to do so, if you ask me.