I don’t think you did your emblem strategy wrong @sleepyhead . I think you’re seeing the paying players increased opportunities play out the same plan you’re following faster.
I am a strong believer in embleming heroes for offense. That is the part of the game you play. D helps with war score and raid arena and that’s it. IMO if the rest of the portions of the game are weak, then those strong portions are meaningless.
For example if you put all your emblems on your D team to keep you in diamond but your offense can barely beat diamond teams, then who cares you can stay in diamond. It is hurting you in the long term.
Same scenario with war. So perhaps by the second half it is taking multiple hits to kill your D, but if your offense can’t kill them back the extra 1-3 attacks it took to kill you don’t come close to off setting the points from poor offense. If you’re geared for attack in the wars you fight you can get 400-500+ points. The D team you’d have by default from offensive embleming won’t come close to giving up as many points unless the teams are so mismatched your power is irrelevant anyway.
Both are especially true as some of the top D heroes you would be embleming up are below average on offense.
I hope that makes sense.
As for the offensive embleming I still do most my damage with 4’s. I went by category and in some cases there were clear-cut favorites. An example would be Sabina over Skittleskull when I barely used Skittles as it was. I focused everything on Sabina then.
I also have some loaded categories. Rogue for example I had Scarlett, Kelile, Domitia, and G Jackal all being used a lot and worthy of emblems. Having 1 hero maxed was too conservative, but sharing amongst all 4 was too liberal. The heroes wouldn’t have enough boost.
I landed on embleming two heroes simultaneously alternating nodes per hero. Working with 2 at the same time seemed to be a fair balance. When Scarlett and Kelile )my only red hitters) were done, I poured it all into Jackal, now I am finally starting Domitia.
When I have deep pools I stopped my 4’s at +18 as the emblems for the last two were better spent on the next hero. I did max certain key heroes to +20 though. This also works on 5’s as I am doing with Lianna and Athena for ranger emblems.
Now by default of finishing those projects my D heroes are getting bumped up as it is their natural turn. Many are all in the 13-15 range now). My D can keep me in diamond if I raid daily. If I don’t it keeps me close enough to raid into it most the time depending on how many days I wait. As certain heroes got stronger I tweaked my D, but even if the D team wasn’t ideal the emblemed heroes for offense I had could keep me where I should be.
I do give heroes tue first node for certain classes too. Mostly fighter, rogue, barbarian, and paladin. In my rogue list I have Danzaburo at +1 but never intended to give him more. I did skip paladin on Cyprian as that first node actually hurts him. So it’s not a hard and fast rule. Say Kashhrek though won’t get +1 as it’s not worth it.
You can also circle back like get a key 5* to +7, go back to another hero like a key 4* to +18, then Keep going on the 5*. I did that a bit as you never know who you’re going to summon. Likewise some key heroes became less key and got reset.
With mono it is a little trickier as you have more heroes of a certain color to emblem, but usually on a mono team every hero has a role but there are 2-3 that are more critical than others. There is usually a key combo that makes the team work and the other heroes supplement those core ones for the combo. Focus on the key core heroes that tue team is built around first. Then go back to the supplemental/auxiliary heroes.
I hope that helps and makes sense. You’re doing it right in my opinion, you just do it slower as a FTP.
comrades! 
yeah, and another benefit of spreading emblems around for offense is being able to compete in more arenas (e.g. 4* Raid Tourneys). great input and advice - great takeaway also is being willing to reset emblems when needed. I reset Margaret for Francine for example, as Francine is also on my defense where Margaret is only used for offense…
Maybe wait until January Costume Chamber, where you will get a costume for your Leo and maybe another 5*. 