I've worked in various trios for the past ten years or so from rock to metal to fusion and I have encountered the same thing in every one of thas bands and this is what helped me some. 1. Taking a closer look at my bass line and my confidence in delivering it. Making that chug really chug etc. 2. Adding more notes, working with arpegios or throwing a little melody under the solo. I have heard a lot of people use chords very well. Me not so much. 3. My tone which ended up being fixed by getting an amp that had greater presence and eq-ing in a way that took up more sonic space. ie more mids and i needed to boost some highs to get more cut. Also looked at using a pick vs fingers in parts to gain more attack which made me sound more present. 4. Finally the guitar player worked on his eq and volume during rythm sections making his tone a little less thick by dropping a little low and dropping the volume a touch. This also had the final effect of making our verse and chorus have more punch, the bass had more definition in the song overall and in the process it left more sonic space in verse and chorus by pulling some low out of the guitar that made the vocals pop more and the tom work on the drums clearer as well. I think it helped me to look at the whole sonic presence of every instrument in the band. Do I have most of my attack and definition in a frequency range that is not being heavily populated by another instrument, repeat for everyone. Tune drums differently, eq on guitar bass and vocals. aphex aural exciters usually used in the studio for vocals worked well with bass and guitar to excite ranges that the other wasnt exciting giving evefyone their little niche frequency range in a subtle but very "felt" way. Thats what I've found to work and watching good engineers live and studio and picking up tips from them was a maor help in trouble shooting those things over time. Every time I start a new project it tends to start running through the same check list and getting everyone to create an effective sound together.