Imo when u have currently a two hand equiped its better to switch to berserk stance and use pummel.
Shield bash is only worth it when u have already a shield equiped.
I use a macro that makes u switch to berserk stance and use pummel when u have a 2h equiped and shield bash when u have a shield equiped:
#showtooltip [nostance:2] Pummel; Shield Bash
/cancelaura Bladestorm
/cancelaura Hand of Protection
/cast [equipped:shield,nostance:3] Shield Bash;[noequipped:shield,nostance:3] Berserker Stance;Pummel
/startattack
#showtooltip Shield Block
/cast [stance:2,equipped:shields] Shield Block; Defensive Stance
/stopmacro [equipped:shields]
/equip The Sun Eater
/equip Crest of the Sha'tar
Replace shield block with w/e. With some testing you should be able to add berserker stance/pummel w/o weapon swapping, just need to play around with it I think.
Could probably combine this somehow with jakkre's macro.