I've also found a BIG difference depending on the oven size. We HAD the smaller 17" oven in our TT. Pizza stones etc. helped but DW wanted a bigger oven so I installed the 21" oven. WHAT A DIFFERENCE. It gives more space between the heat shield and rack and more space between the burner and oven bottom. Now we can cook with much less concern on stuff burning. BTW BOTH ovens were about 50F low on temp compared to the dial. 350 on the dial was really 300.
So, if you have the smaller oven, yes, IMHO you absolutely need a pizza stone, bricks or something to distribute the heat. your not alone, your not a bad cook, it's the nature of the beast!!
To solve the dial error I just measured the actual temp for each dial position and then using my Ptouch labeler made new temp labels for each temp.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!