the arena was definately alot harder 6 or so months ago, BOT teams were added to help progression as alot of the player base was stuck with that mission alone let alone reaching higher gold tiers
build your team with the aim of the team complementing each other eg speed lead aura for arena champ, decrease defence debuffer, then say increase attack or stun or sleep then in comes a AOE nuker say Kael
as your arena team gets stronger you will find your progression through the lower arena tiers will jump and become easier
speed is king in arena however in saying that if you have the champs to survive the opponents going first and go 2nd you can still get the win that way - i had no speed lead for so long in the arena that i build my arena team around defence and surviving the first attacks then my team would go and rip the opponents team apart.
good luck and trust me we all were feeling you are right now at some point, it only takes that 1 champ to turn things around