Well, I'm actually going to disagree and argue that increased strength does in fact increase punching power, regardless of the level of technique. People try to make punching out to be some mystical thing that is unaffected by the muscular system when in fact it's just a kinetic chaining of movements and skeletal muscular actions leading up to an impact force at the end.
The more powerfully your agonistic muscles can fire, in the correct sequence, while simultaneously turning off your antagonistic muscles, the more powerfully/fast your are going to move. And, because an impact is a collision in which you come into contact with another mass, there is going to be resistance at the point of impact in any strike. Yes, you can maximize leverage under perfect conditions, but even then you must have the requisite muscular strength of absorb the rebound force your encounter and, if you really want devastating power, must be able to continue driving through that mass/rebound force.
Now, that's not to say that strength will improve power more efficiently than technique, it won't. Maximizing leverage, kinetic linkage, and relaxed explosiveness (since kinetic energy is ultimately more dependent on speed than on mass) alone can literally double a person's striking power in a single training session (if done correctly); pretty much impossible to duplicate in the same time frame with strength gains. The issues of accuracy, timing, and judgement of distance also play critical roles in the effectiveness of a punch.
Because of this, I would generally place technical/mechanical training as first priority; then developing the attributes of Judgement, Speed, Timing, Accuracy, and Rhythm second; then conditioning work (anaerobic and aerobic endurance) third; and strength/power 4th in regards to applied punching power. Again, that's not because gaining strength won't increase power, but more so because unless you are talking about simply throwing the hardest punch possible once, on a stationary target, focusing on those other attributes will give you a greater return on investment for your time spent on them.
Maximal strength training is to combat athletes what dietary supplements are to physique athletes, a nice and useful supplemental tool, but not meant to replace the foundational elements of a solid training regime.