I totally agree that staying dry in all conditions is a losing battle. Of course, to some extent staying dry and staying warm are the same thing. If you're wet enough, long enough you will feel cold, even if the air temp is 70 degrees. It's always about finding that elusive balance between sweat and wet, and also balance body heat and the cold air.

In a cold rain, I'll wear a waterproof outer layer. Under that I wear a cotton jersey, with a wicking shirt under that. I know--everybody says don't ever wear cotton in cold weather. But in this case, the waterproof shell keeps you dry but makes you sweat. The wicking layer keeps your skin driy. The cotton midlayer absorbs and holds the sweat. When I get to my destination, I'm dry as toast, even though the cotton jersey is wringing wet with sweat.

The fact that a 100% waterproof material needs a dwr coating to protect it from the rain is quite ironic, and is precisely why goretex is way behind other fabrics now. Was great in our grandparents time, unfortunatly with a few billion in marketing over the years, people still think its great.

Yes it needs to be reapplied when it wears off.

Without it your 100% waterproof garment is still waterproof. As I mentioned before, it just loses it's breathability and you get humidity inside the jacket which, when combined with chilly air, makes clamminess.

I have reapplied the DWR finish to Goretex with a warm iron and with Nikwax (both recomended by Gore) but the beading effect is never as good as new.
Without effective beading the fabric becomes sodden and non-breathable. Riding for 6 hrs in heavy rain with a sodden jacket is not much fun. It remains waterproof but you get more condensation and the jacket takes ages to dry out.
These days I use gortex as a summer showerproof carry-along and for tours. I prefer whenever possible to use a non-waterproof windproof smock, these can cope with a little light rain if its not cold.

For everyday all-weather riding below 16C I use Paramo which is the Grandaddy of softshell systems and storm-proof to expedition standards. The beading can be restored quite effectively and it always dries quickly. The only dissadvantages are that it is quite warm compared to most waterproofs (but not in a clammy way) and it is quite bulky to stash but I wear rather than carry it.

BTW, depending on where you work -- you may find that "presentable" in the Seattle area is a pretty low bar. Workplace attire is pretty casual in most places...and even in "nice" places your typical REI attire is about all you need. And bikers changing in the washroom at work would not be unusual, either.

Just the other day I got in an elevator in a downtown office building w/a young woman nicely attired in semi-dressy work clothes, including a skirt and nice dressy shoes...carrying an expensive designer handbag...and wearing a full-frame, fully loaded backback. Did she hike to work? Was she going backpacking on her lunch hour? Leaving on a snowshoe expedition after work?

So, don't worry about changing at work. You'll fit right in.