Save dc on my reserve feat

[tharnok]

im got a Bard/ Stormsinger/ Disonant Chord lvl 20, my main damage is using my Stormbolt reserve feat, but the DC the enemy have to save against is 20, and thats using Storm of Vengence as the base.
Now i been gone a few years and just resently came back, but im sure the save dc was higher, the curent save makes it nearly useless since everything i need to fight to get xp can save against it.
looks like the save dc is curently spell lvl for damage +11 and its forgets my cha modifier, if im not wrong Reserve feats save DC if they alove one shoud be 10+ spell level they use for dmg + main casting modifier.

Also sometimes the reserve feat dc fluctuate if i just use one of my Stormsinger songs getting their save Dc for 1-3 cast then turn normal or close to em since i seen save dc 33 and 30 on my stormbolt, after using the same Stormsinger song and with same buffs one.

With greetings tharnok