Heavy Fort is not required.
However, no other item will do as much to reduce incoming melee damage as a heavy fort item will...
Heavy fort will do more for you than a ton of extra HP will.
In theory a high enough AC would be better. But in actuality, getting a high enough AC is so difficult that is is not worth even trying.
Equip your toon however you wish IMO.
Part of the game is choosing what wearable item (or weapon...etc.) is more useful to you in which situation.
But against melee attacks, there really is nothing better than Heavy Fort to wear IMO.
I suppose certain situations would make you decide to wear something else instead...but those situations would be very few.
(for instance, I am strugglng with how to have heavy fort at the same time I wear my Big Top....even though I rarely use the Big Top, it puts me in a vulnerable position to have to remove my Minos Helm.... just part of the game...choices)
But...as I stated before... it is not required.
But it's one of the best things you can wear....so why not wear it? (I have bought many taps off the AH for what even my broke butt considers affordable....but I understand a brand new player might not be able to afford them. But lots of XP to be got while killing for taps...well worth the time IMO)
Edit: during the Crystal Cove event, many of us took off our Minos Helms to wear pirate hats.....and got our butts handed to us! Actually took some of us awhile to realise just why we were suddenly so much more squishy than usual.