If an II of 1 is usually the best scenario, it is rarely the only sufficient scenario. The goal is to meet the latency and throughput goal. To this extent, various combinations of II and unroll factor are often sufficient.
The optimization methodology and techniques presented in this guide should help meet most goals. The HLS compiler also supports many more optimization options which can be useful under specific circumstances. A complete reference of these optimizations can be found in HLS Pragmas.