I'm not going to comment on whether a playstyle is fun or boring, since that's pretty subjective, but I disagree with your statement that blasters aren't that strong. They're great all-rounders in terms of clip size, range, bullet speed, hitbox size, and knockback (not too much, not too little for pure gunners). DPS is less than alchemers on single targets, but it's not an enormous difference (at least, not enough to go from not powerful to powerful in my opinion). Blaster DPS is also more consistent and, from my experience, it's easier to hit multiple targets with a single bullet.

I would recommend Riftlocker instead of Gilded Griffin, mostly because the large hitbox makes it a lot easier to hit piercing-weak enemies. Arcana is great, but I prefer using alchs because the charge lets you take out turrets in one go. You could always make Arcana first before slowly expanding to alchs or something.

I agree that you should give Magnus guns a try. Any of them are great, including Iron Slug. You'd need to use the Perfect Mask of Seerus to get the most out of them since they're largely charge-oriented, but they're the best way to clear crowds of monsters quickly and efficiently.

Callahan is pretty good (one of my favourite guns too) but as you've already mentioned you got some lag and I don't think it's gonna work too well for you since most pierce-weak enemies dodge and with this you have to aim. The iron slug on the other hand can one-shot any monster that's affected by knockback if aimed right, it's not really about having specialised damage it's about its style. Because of its normal damage though it proves to be the best weapon in dealing with D&N, lumbers, lichen colonies, black kats all at once unlike the winter grave and callahan it's good EVERYWHERE. Also you don't have a normal weapon and as you said you're going to get riftlocker evantually and I don't think you want to have 3 piercing weapons and one elemental and one shadow weapon with no normal weapons. Having a normal damage weapon can be pretty useful in many cases too like when battling tortodrones, vana's mask, crowds of different enemies inside a vortex, levels with many monster families not weak to the same damage type. When I had an iron slug (it was level 1, I never leveled my stuff then but it still one-shot or two-shot any monster, there's a discussion I found then that made me craft it, it stated that its charge had more damage than ahceron against slimes/gremlins if aimed right of course) I used it as my main weapon. Now I have a callahan and a winter grave but I never use them because they aren't that good compared to my final flourish/acheron when it comes to the same scenario.