Final level mortar is just another 10% increase which does nothing obviously. Mortars were already one of the weaker defenses, so a new level would do nothing really. Given that scattershots attack much faster and have 4x the dps, this is an obsolete defense. They should at least buff it and barch so that both remain viable.
Another level of valkyries and another level of weak increase. For TH11, you only gain 10% of stats which is nothing. Heck, lvl7 which gains almost 20% extra stats cannot be felt. This is why I keep asking for >33% growth per level because anything less than that cannot be felt.
I used a hammer to upgrade my lvl13 mortar and used the same builder to upgrade another lvl12 mortar. The 3 mortars I have upgrading are all going to lvl12 (TH12) and I plan to use hammers/books exclusively to max out my mortars because they are the longest upgrade I have remaining. Besides mortars, I have one level of cannons, archer towers and some traps remaining. I will most likely max out before end of May and looking at my base in May 2019, it is some crazy growth. I base wasn’t even around in May 2018! The before and after pics is going to shock many.