What is the Ti build you have in the Merlin?
Wire gauge and coil diameter, tell me you are NOT still using Silica as a wick. That would have a lot to do with the poor vape quality...
What is wrong with using Silica? I use it almost exclusively.
The test to try here is once a coil is wound and wicked - prime it so that the wicking material is translucent. (both Silica and Cotton will do this, IDK about other materials as I have not tried them).
Once the tank is reassembled try it out. If the vapor production is good for a half dozen or more pulls and then starts dropping off then it is rather obvious that you have a wicking problem as the good pulls were from the juice you wicked the coil with and your setup was not able to replace it.
Cotton and I've heard Rayon wick better than Silica. If your coil is getting dry it will hit "temperature protection" quicker than if it has full contact with juice and your wick.