@lxskllr, i think part of the problem is what you think is a high tie in point (tip) isn't. When you are going out against your tip, you are adding more and more side pull, which fights against you. If you are using the climb line for support like you usually have to, it gets harder and harder the further you go, exactly like sling angles in rigging. The smaller the angle, the easier it is. So your goal is to always set yourself up with easier angles, so you work smart not just hard. With srt, you can simply redirect your line, which simply means you can use a number of ways to get your line over where you want to be, then you will be able to move there much easier.
With doubled rope you don't have as many options but it still can be done (srt just gives you more options). You can simply double crotch, set up an m or vee rig, e.t.c, but if you can't go any further, you need to to get another line above where you gotta go. A great way to do this is use the tail end of your line, throw it over another limb farther out and above where you want, and then climb on that. The two different angles will really stabilize your positioning too.
If you are absolutely dead set on climbing doubled rope, you can also get around trying to isolate around limbs by lobbing your throw weight up over the limb way up there, pulling up a single line with a pulley, ring, locking crab, e.t.c, and have your doubled line in that. You then tie it off at the base of the tree, which is called a basal anchor. You double the force at the tip, but this usually isn't a problem because it's compression loading. Always bounce test every tip, simply get ready to climb and bounce into your harness. This will seat the single line by forcing small branches out of the way, and will verify that it can hold your weight before you commit to it.