There is a theoretical limit to how quickly you can heat things, regardless of the denaturing and scorching issues.
The speed at which you can raise the temperature of your mash depends primarily on two things. 1: How much energy you can put into the system (IE, how efficient is your heating element) and 2: How much wort passes across the heating element in a given time period. Let's use some examples:
1 - Your pump runs fairly slow, basically a trickle. A lower wattage element has plenty of time to heat wort as it passes without dumping energy (heat) into the system faster than it can make it up (reheat the element). The lower pump speeds mean a longer time until the system is up to temperature.
2 - Your pump runs fairly quickly. You put in a massive element that has zero issue holding temperature. You will quickly reach your target temperature.
Both of these scenarios should have little issue with scorcing the wort as there is a balance between the amount of heat being applied and the time that it is being applied for. Unfortunately, there is a limit to the speed at which we can recirculate wort without causing major issues in the mash. Given that limit, there is a point of diminishing returns and eventually negative returns when it comes to larger sized elements. I'm not sure where that point actually is, but we must acknowledge it exists.
I run a HERMS so I can't really tell you what to do, but if you do get a bigger element I'd run it on manual mode at a mid-range percentage for a while and see how your results change. 1*/min is not too shabby, and may be pushing the theoretical maximum rate you can safely get to at reasonable pump flows.
-Kevin