I find it hilarious that early on in this league a lot of people were specifically shaping and running maps like racecourse (though it does still have an excellent layout) and cemetery because they had multiple bosses, because bosses drop much more and better loot than other monsters.
It is also a very build dependent thing, I know my league starter (Elemental Blade Vortex Inquisitor) hardly found bosses much different than normal monsters when I prepped 20 stacks and power charges. But if you're running a build that clears the screen when you attack/cast, of course it's going to struggle with single target, if it didn't I think that would be a bigger problem.
I also think bosses should give much less experience than super quickly killing large amounts of weaker monsters. Killing a boss feels like it should be more about loot than experience, and I think giving players that choice of whether they just want the experience or want more loot is a fine thing to do.
That said, yes, perhaps bosses could use a slight buff in terms of both experience and loot. I actually feel like the number and rarity of items dropped by bosses is fine, but I think some other kind of reward would help players decide whether they are worth killing or not, especially since many people filter out basically all rares now anyway. Something like moving a lot of divination cards, or introducing new ones and making them only drop from bosses, or giving bosses a set chance to drop a map every time (33-50% for example), perhaps divided by the number of bosses (so that farming maps with 3+ bosses exclusively doesn't become a thing).
It is absurd that a map boss gives roughly as much experience as half of a magic monster pack. And something similar in loots (though it is easier to setup a culling IIR skill, I guess, if you want to bother). Extra 20% chance for a map of up to two tiers higher is not really worth the hassle since these days one can reliably sustain T14+ with just alch and go (still having plenty lots of 15 and 16).