I have never glued my rock together. I personnally does like the look of the epoxy. It was gray, and stayed gray. coralline wouldn't cover it, and believe it or not. I does break off. I tried it a couple times a few years back to put a could of corals on rock. My turbo snail just plowed them over.
Second reason I don't glue rock together is you don't know what coral you may find down the road. You may have to move some rock around to get it where you want it. If your rocks are glued together that would be harder to do. Or if you get a fish that is very agressive to newer fish, you might have to move some rocks around.
Getting your rock to stay put, just takes some time and creativeity. You have to look at the rock like puzzle pieces, and see what will fit where. and always use a 3 prong structure. Also I you use the wieght of the rocks to push against the other rocks, You are more likely to suceed.
These are pictures of one of my 75gallons, This has been up for a few years. Never had even one rock fall out of place.
This is my 180, This has been up for almost a year, and same is true here, never has a rock so much as moved, and I have a diamond goby in this one.
No glue, wires, zip ties, just fitting the pieces together and use gravity to hold it together, Kind of like when they designed the St.Louis Arch.