Two thoughts -
Please post a full set of test results for your pool water. Talking about specific chemical levels in isolation does no good.
Myths about pH/Heaters/Etc
There is no such thing as a "bullseye pH" or "optimal pH" or any such thing as it relates to specific equipment in general or heaters in particular. Your heater is much more likely to not work because of a system issue (not enough gas pressure, bad sensor reading, improper flow, etc, etc) than a chemistry issue. People think that because there is science surrounding corrosion in one part of life, eg, road salt corrodes my chrome bumper OR calcium scales out inside my SWG, etc, etc, that it necessarily applies exactly to all other aspect of life. Simply untrue. Corrosion or scaling inside of a heater are very specific phenomena that have their limits and conditions when those types of processes apply. Just saying "my pH may be high or out of range" is not specific enough to be able to know what impact that would have on a heater or if there would be any impact at all. This is why a FULL SET of test results is important.
The two primary chemical processes that could potentially kill a heater's copper heat exchanger are scaling of calcium carbonate because the CSI of the water is too positive OR etching (dissolution) of the copper surface due to very low pH. If you post test results, then it can easily be determined if scaling is possible. Note that I said "possible" ... while saturation indices tell us what is possible they do NOT predict what will happen exactly. As for copper being etched or removed, that is almost totally impossible at normal pool pH ranges (7.0-8.2). Both bare copper metal and it's various oxides (passivation layers) are stable in that pH range. Only exposure to very acidic water (pH < 6.8) for long periods of time would degrade the copper metal surface. This is typically the case when people throw trichlor pucks in their skimmer - trichlor is very acidic and when the pump isn't running, the water in skimmer becomes very corrosive and acidic and then, when the pump turns on, a slug of low pH water hits the heater and does damage. This is one very good reason why chemicals should never be dumped into the skimmer.