You might classify this report as a feature suggestion, but since developers were reiterating the intention to make wardens formidable, I am creating this issue anyway.

How to reproduce

Tower near a warden by 4.5 blocks high (for example using slabs), anger the warden, press shift and land a hit on it. The warden tries to attack the player but in vain.

If you tower by 4 blocks high, the warden can hit you. Otherwise if you tower by 4.5 blocks or higher but keep standing, both you and the warden will fail to reach each other. Warden seems to be designed to reach far but maybe not far enough.