Need advice about Cards, LAWs, units

So far the game has suckered me into spending a ton of money on the game, and it has led me to question a few things. So here I am asking the community for input and advice.

All these URs I'm collecting to advance to GURs, whats the point? They won't be as powerful as the next set of cards with the temporary 10x damage against the AWs. Is it even possible to defeat a LAW without any of the event cards in 10-15 BPs?

I started played about halfway through the alchemist event and pretty much didn't get anything out of it, but on the last event I managed to rank to top 500 with 2 GUR Demises which let me kill the LAW in 10-15 turns. New event comes up, and I take my team out for a stroll and vala, my GUR Demises only deal 29k damage. Literally everything I worked for the last event turned to ash. I won't even be able to defeat a LAW at this point.

What am I missing here? Is my team not good enough? Do I really need to spend money on the event and get the new cards to rank to top 500s?

Current team: GUR Demise lvl 90 skill 10, GUR Demise lvl 90 skill 10, UR Conjurer level 70 skill 10, UR Prometheus lvl 70 skill 10. Not enough deck cost to put in a 5th card.

Is it because I'm going with 800% single target as my main attacker that I am having so much trouble once the card's AW buff phases out? Before I can take out AW's or LAW's support cards in one or two regular hits and just focus the abillity procs on the AW/LAW. Should instead go for AOE instead or is this normal and I should just pour BPs like water and drown the LAW and AW to death?

or should I just treat this like a collector thing and the point is to grab all the cards and be the very best that no one ever was and don't question anything?

Or is there a magical team that is able to take down AWs and LAWs without the buff against them?

I have a crap ton of URs, but no 2nd copies to make them into GURs, I am going to list some of the most useful stuff I have in hopes that someone with more experience is able to give out some pointers:

GURs: Demise x2, Mildred x1

URs: Cagliostro x3, Assault Angel x2, Anat, Kukunochi x2, Hijiri-no-Kami, Conjurer, Bookworm, Launcher, Redeye, Premium Prize, Prometheus, Shiroyagi, Shirley x3, Lover Demon, Wadatsumi, Magma.

GSRs: Assasult Reporter x2, Fiona x3, Griffin.

SRs: I got 108 of them, all kinds of 250% AOE, critical damage to all, critical damage to single, turn skippers, buffers.

Thanks a lot guys for taking your time to help out a newbie.