Keep in mind that we're talking about 10-15 million Cr/h, or thrice that if you do the LYR grind. (Which, to be frank, in my opinion shouldn't be a thing.)Exploration already go overbuffed around the time of the introduction of the FSS.
Regardless of any arguments about "skill" and whatnot, there is the element of risk that you go many hours without selling your data, and thus, if you do lose it, you lose many more hours of progress than any other career would.
For example, combat is high risk, high reward, small punishment if you fail. Exploration is low risk, tiny reward, and the harshest punishment if you fail.
Personally, what I would do for a more comprehensive rebalance would be:
1. Change the LYR bonus to something else, since as long as it's there, it'll unbalance exploration regardless of what you do. The PowerPlay folks could probably prefer a bonus more useful for PowerPlay too.
2. Make the "first discovered / mapped by" tags instant, like they already are with Codex tags, and turn the scan's credit value into vouchers, to be redeemed when docked, and lost on ship destruction. Alternatively, make Codex tags not instant instead.
3. Rebalance payout values, right now they are quite all over the place; see rarities, for example.
4. Boost first discovery bonuses, to encourage doing that instead of farming already-known bodies over and over. (See the recent CG.)
5. Adjust DSS payouts, players should not feel compelled to waste time flying to planets not to explore them, but only to squeeze more credits out of a planet. Players should want to DSS a planet to reveal the POIs there to explore.
6. Increase the exploration rank requirements, because it's too quick to Elite already.
7. Change Prof. Palin's 5,000 ly requirement to something else, because a combat-based engineer shouldn't have a travel(!) requirement, and all it does is just make combat pilots dislike exploration.
Well hey, I don't expect Frontier to give much thought to rebalancing exploration, but at least I've made my suggestions.