Heartfelt beads work very well, but they aren't miracle workers. If a humidor is too leaky and the surrounding environment is too dry, they simply cannot adequately maintain RH and you need to fix the leak or get a new humidor.
For a lesser problem, HF beads or Bovedas will probably keep the cigars safe and smokable, but perhaps not as high as the devices are rated for. In such a case, you might use 70% HF beads, or Bovedas at 69% to 72%, just to maintain ~65% RH. I would not recommend higher-RH devices such as 75% Bovedas, unless you are willing to check the RH, without fail, every single day; if the home atmosphere's RH rises, as it will in spring most places, you could quickly end up with overly moist cigars and possibly a mold problem. Fortunately, Bovedas can be recharged a few times and HF beads can be recharged as often as necessary; it's just a little more work to do.