Queen of Thorns isnt right, something wasnt thought out correctly with her, or she was made with something else in mind. People in charge of balance should solely play QoT instead of demigods which are regarded as very strong.
Her health, armor, damage, and rate of fire is pathetic. Shield is powerful especially early game but its in a different form than her only other decent skill Ground Spikes.
Her other skills especially Uproot are just terribad. They are poor skills to begin with but when you factor in thier high mana costs and fact that they require form switching to use its just abysmal.
If you are an awesome form switcher you can get QoT to work for you if you are able to get good at the early rush... provided you are on a map that allows an early rush, otherwise you are s.out.o.luck against a competent team.
2 suggestions off the top of my head would be make shamblers fight in close melee and buff them a bit so when you fight in close you can mulch them effectively using thier aoe damage.
then for open form make uproot drain life like the rooks spell.
maybe the devs just dont want QoT to be good otherwise everyone will be playing her to look at boobies