BWD: Maloriak, Atramedes, Chimaeron
BoT: Halfus (hard drakes), Ascendants (dps gate boss, either you burn him down in time or you don't)
BoT: Chogall (easiest of the final bosses)
BWD: Nefarian (hardest of the normal mode bosses)
If Halfus has frenzy, shadow nova and mortal strike for your first lockout, go to blackwing descent, you will find maloriak easier.
Conclave and omnotron are very simple execution fights. Halfus and Magmaw are dps checks as well as orientation checks. From there on in, you will be wanting your 5 dps (assuming you 2 tank/3 heal the places which is to be recommended) to be pulling 12-16k dps each to beat the berserks/soft enrages.
also i wouldnt suggest hitting magmaw without a player who can reliably slow the worms like a hunter with frost trap. if you dont have a reliable slow then you will need to tank them with some serious aoe dps
What's been responded here is very accurate so I wont get into the order of progression, but since you said that your attempts on magmaw and halfus didnt went exactly well, I'd like to point out awareness of the general state of your raid, you can ask yourself the following:
what's my raids composition, do I have a good enough melee/ranged ratio? (this specifically for magmaw, cuz u need good ranged and good snares)
what's the average dps of my dps crew? does every1 exceed 10k dps?
what's the average hps of my healers?
Is every1 familiar with the boss strategy?
If you can answer all these questions in a positive manner, you shoudlnt have much trouble with any of the entry level encounters (except maybe halfus on some weeks).