My elec/elec brute has been without stamina for a long time now I have assault and tactics also I have not sloted for endurance anywere other then assault and tactics and its really not been a problem as long as im paying attention my endurance doesnt drop and I dont have to stop attacking.
Having said this if i had to exemp down to under level 30 for an SF or for that matter to anything under level 35 things suck a bit but at 50 its great
One thing to note is that I went stamina less before IOs and before i could use HOs but I am now using a few of them.
Must haves for stamina less are Power Sink, Conserve Power and Power Surge. Sometimes if i slip up and miss time something my endurance will drop or be close so going without stamina does require more attention but if this happens hit power surge as it gives a good endurance recovery boost and if your toggles just went down will hopefully keep you alive.
Another little note is that if you have aid self and you are very good with timing you can compleatly avoid the downside to power surge. Just as its about to drop hit power sink in the mob to get your endurnace back to full. hopefully power surge will have EMPd the mob around you (this happens more often if you slot some Acc in) and you can hit aid self and before they can attack again you are fully toggled and at full health. This works best if you have something like demonic or a few lucks for the moment before power surge goes down as any dot damage will kill you.
Having said all this all builds should probebly be tested out on the test server first and i cant account for fires endurance cost though I assume that it would more likely be lower then elec and it probebly isnt a good toon to be playing drunk/tired/other

Hope this helps and good luck!