As somebody said, the main problem is that Reg is bad at Domination games. Its just not going to be holding flags against many DGs for most of the game.
But TB really shouldnt be a problem for Reg. I LOVE facing TBs as Reg.
One thing to say right away is that you arent a 1v1 DG, especially early in the game. Really you dont want to be fighting 1v1 vs much until at least the midgame. Your strength is sitting back and doing damage while some other DG on your team is up close and taking the damage. Of course, the other team knows this and will be trying to get around this, but thats the situation you are going for.
For this reason, I dont ever like the advice of taking Blood of the Fallen for Reg. I always take Anklets because speed is too important for a DG that doesnt want to be under fire much. You just cant slug it out even with Blood early in the game, so get Anklets to skirmish. Basically you stand behind another DG and shoot away while he is in close. When they try and come for you, use your superior speed to get away while the other DG hammers away at them chasing you. As soon as they give up the chase, go back to shooting at them. Thats the template for how I try and set things up.
Its possible with a mines build to go BoF and do OK, but I just dont like the possibility of most DGs being faster than me on a fragile DG.
Now if I want to go 1v1 against a TB, this is what I do:
Hit them with Snipe before the fight starts. Hit them with MoB as soon as they get in range. Combined with the earlier Snipe, this should give you a health advantage as well as a speed advantage (you know that they will have to trigger MoB pretty much right away). Hammer away or mine or whatever until you need to get away. Remember that since you have a tool that has the best range (Snipe, which should have cooled down by the end of the fight), you can disengage, get space, and Snipe whenever you need to. It also means that you should be winning fights where you both get down to very low life - you can pull away and basically hit from infinite range, while they cant.
I don't see how a TB would beat you 1 on 1 unless you're dumb enough to not get mines.
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An auto attack build is also very powerful. Mines are by no means a necessity for Reg. In fact, I like being auto attack better than mines against TB. Since a TB uses ranged attacks, mines arent so good. They can avoid them and still hit you with ranged hits (something a melee DG really cant - they cant take the time to run around the mines and they dont want to charge through them).