Morning,
Personally I love boros style dmg/lifegain style decks (ill post my current deck below, though it is naya the concept is exactly wut ur trying to achieve i think), but my advice is always avoid spells that only net u life with little to no other benefit (ie rest for the weary). Life gain by itself is practically pointless unless ur going for a
test of endurance 
/
felidar sovereign 
win, seriously when
reveillark 
and
marytr of sands 
were in standard together i would upwards of 50 life in standard games, and still lose because i lacked a decent when con. But life gain stapled to removal like
faith's fetters 
or a decent body
loxodon heirarch 
/
kitchen finks 
/
obstinate baloth 
and of course
lifelinkers 
are all solid cards.
If you're planning on sticking to ur mono-white build I'd certainly consider finding a playset of
martyr of sands 
as they are humans and ur can constantly recur them by
bli 
nk 
ing 
ur angel of glory's rise and gaining crap-tons of life.
emeria the sky ruin 
also belongs in any mono white deck with a high mana curve, and considering ur curve id include some artifact ramp like
mindstone 
marble diamond 
gilded lotus 
ect just so u can land those bombs quicker.
If ur reconsidering ur boros style approach for dmg and life gain heres my list maybe u can get some ideas
4
Tamanoa 
4
Balefire Liege 
3 Naya Charm 
4 Naya Hushblade 
3 Duergar Hedge-Mage 
4 Trace of Abundance 
3 Brightflame 
2 Rith's Charm 
3 Lightning Helix 
4 Searing Meditation 
3 Ajani Vengeant 
4 City of Brass 
2 Battlefield Forge 
2 Brushland 
2 Karplusan Forest 
5 Plains 
4 Mountain 
4 Forest 
the general idea here is that everything i play triggers balefire, which in turn triggers tamanao, which lets me gain loads of life while sucking the life out of my opponents. (btw the pain lands also trigger tamanao so it negates the whole "pain" part). Looking at it now the list is a lil dated but i m waiting for boros to show us wut it has for us in gatecrash before i work on improving it.
ok i think ive said enough, good luck
ps- u cant cloudshift ur creature in response to a worldfire to avoid the worldfire. Wut would happen is ur opponent would say "9 mana worldfire" then u say "one mana cloudshift avacyn" ur cloudshift would target and resolve first, which means the avacyn would pop out of the battlefield then return before worldfire resolves, so she'd shift back onto the battlefield and worldfire would wipe her and everything else out. Now you could turn to mist 
avacyn, she'd be exiled until ur opponent's end step and then return to a broken, decimated board state wholely unscathed. That being said turn to mist is a terrible card, stick to the o-ring trick, lol
