So, the changes are as follows: now (just like tooltips were saying all along - since what happened is a bug fix) enchantments will proc both from light/heavy attacks, and from any damage dealt by weapon abilities (before Murkmire, only ground AoEs such as Endless Hail or Wall of Elements were about to proc them by continuously doing damage). So, in the context of DW, now not only light attacks will proc it, but also Twin Slashes and morphs. As a result, as long as Twin Slashes applied to the target, enchantments will proc (one per damage tick, whichever is off cooldown, favoring main hand if both are). That made possible to apply Slashes, swap bars and make sure that damage/absorb enchantment from DW bar will proc every 4 seconds (every 2 seconds for infused enchantments).

Now, whether to switch, will depend on your needs. If you want to boost strictly single target damage - double infused will probably pull ahead (poison or absorb glyph main hand, berserker off hand, or alternatively can put berserker on bow and absorb on off hand). That will give you more glyph damage on the target, but only the target you're attacking; as a tradeoff, you will lose ~200 weapon damage - which will reduce your AoE and healing. Now, if you want to boost your AoE damage, you may want to keep Nirnhoned, more so that weapon damage multiplier will receive a 8% boost this patch (3% from medium armor buff, 5% from Minor Brutality provided in the group by DKs).

@Joxer61 , with tanks, it's just the consequence of how enchants work now; say, if you want to keep Crusher and Weakening on target, now you can do it much easier by going for infused DW backbar, and since Twin Slashes now proc both glyphs after bar swap, you can ensure good uptime on both - just by making sure that Twin Slashes is ticking.