Based on the leaked info, the necron decurion, basically a detachment made up of other formations, appears to have been specifically designed to break your scared brains. Your stopgap nonsolutions are about to die tired and confused.
Make people bring battleforged armies. You don't need more words. Stop worrying about number of "sources" or detachments. You just confuse yourself. Especially when you randomly give tyranids exceptions just because... actually I have no idea why you were ever doing that.
Stop trying to redesign the game by rewriting invisibility or rerollable saves. Not necessary.
Stop trying to overmanage lords of war and superheavies. And stop tryin to discourage them by including Escalation widgets. They are points sinks that can only control a small portion of the table, but are fun and take skill to use. All take-all-comers (TAC) armies should be able to deal with them if you can ALSO expect TAC armies to handle a 5-knight army. Just temporarily ban the revenant reaver and warhound (or don't, whatever). Based on the TranCtan and Vault nerfs theyll get their turn eventually too.
Design a better hobbyist prize category with prize support/trophies/bragging rights rivaling Top Asshat prize. and/or keep doing the A and B tier split brackets on day 2/games 4-6.
Someone please point out any issues that would still arise and I will consider them.