I don’t think the current incarnation of healing in EVE online is ideal, due to its all-or-nothing nature. Either you have the DPS/alpha to break the enemy fleet, or you don’t and nothing dies. This problem isn’t easy to deal with simply by applying stat nerfs to logi, though - there’s a pretty thin line between “logi is so good it dominates the meta” and “logi is so bad no one uses it.” This is essentially what CCP were trying to solve for supercapital combat with diminishing returns, but this won’t have much influence on subcapital fights, nor should it, since it would only kick in at fleet sizes >100 where ships just get alpha’d anyway. I think the best way to make logi less dominant without nerfing it into the ground would be to cause buffer and resist modules to generate heat and take heat damage when absorbing very high DPS.
The intention wouldn’t be to change anything about PvE or solo combat, which is why there would be a “threshold” below which heat damage doesn’t occur. However, if ships began to lose extenders, plates, and hardeners after getting primaried in a fleet fight and taking damage around 4 times their EHP in <30 seconds, this would prevent the kind of stalemates that are all too common in medium-scale fleet combat. Logi would still be useful for extending the lifespan of fleet ships, but it would be nearly impossible to keep someone alive forever. Besides leading to more pretty space explosions, I think this change would also introduce more variety into the meta by reducing the importance of alpha strike, which has currently led to a pretty stagnant meta of arty Machs for medium fights, and Muninns, Feroxes, or Eagles for big ones.