I will occasionally write travel theme essays. On the subject of Wiesbaden and where one might stay.....you end with four categories of hotels.
Premium class: The Nassauer Hof, Hotel Hansa, the Blu Schwarzer, and the Dorint all fit into this category. It's hard to find anyone who complains about a stay in Wiesbaden at these four hotels. Cost? Minimum of 100 Euro a night, and the Nassauer Hof will typically be a 200-or-more Euro a night place.
Decent Three-Star class: Motel One, the B and B Hotel, Hotel Drei Lilien, and Ibis. I could probably throw another dozen onto the list.....you can find a good listing and comments off Trip Adviser.
Cheap places: NH Wiesbaden, City Hotel, Hotel am Kochbrunnen. These are places where you can probably get a room in the 60-Euro range. They aren't necessarily bad places....just places without character and simply considered average.
Losers: I won't bother with names.....you can analyze data on Trip Adviser and come to conclusions.
The thing is....Wiesbaden is close enough to Mainz and Eltville am Rhein....that you could stay at hotels with either of these cities and enjoy day-trips to Wiesbaden as well. The 6500-area rail and bus ticket which gives you all-day access to Wiesbaden and Mainz is 6.3 Euro each. Eltville is outside of that zone but it's got different features on the plus-side. If you could get rooms at Kloster Erberbach, it'd be a unique life experience....but it'd be a premium price that you'd pay (you'd have to make reservations six months ahead of time because it's not a large place). I'd also put the Das Spritzenhaus on the list....but again, six months ahead on scheduling a room.
Distance convenience? No matter where you stay in Wiesbaden....it's a 20-minute walk at most....to any of the typical tourist sites. That's the one key advantage of the small city image.
Bad deals? Well....there are a couple of minor hotels in the region that have noted that they are credit card-friendly hotels.....only to have the guest discover upon arrival that they aren't friendly....or when the whole trip is finished and you are ready to pay.....they refuse the credit card and want you to pay cash. Well....if you arrive to discover this....smile and walk away. If they've pulled the trick on the last morning and demand 1,200 Euro in cash (when they said they'd take credit cards).....then go and call the cops. A short conversation will occur, and the hotel manager will be pressured into accepting the credit card. Why such behavior? They'd like to have cash....to avoid identifying income and taxation. It's illegal behavior but I can think of two hotels in Wiesbaden who've done this in the past three years. Larger hotels don't do stupid crap like this.....these are mostly the forty-to-sixty room places (on the cheaper side).
Outlying hotels? That's one of the other things that you could examine. Niederhausen is a smaller town to the north of Wiesbaden, which has the Ramada. Great place by the autobahn. Negative is that there is no public transportation around the hotel (you need a car). Pricing for this hotel is usually in the 60-Euro range. The Wald Hotel in Eppstein (about 25 minutes driving from Wiesbaden) is another great place.....placed in a wooded area....with price range near 80-Euro a night. Again, public transportation is a negative so you need a car.
How much sight-seeing can you make out of a Wiesbaden stay? If you have a car, and make some use of public transportation.....ten days worth.
Most of what Wiesbaden has to offer (the park, Casino, down-town, etc) can be seen over a two-day period. Mainz.....maybe 1.5 days. A trip up to Eltville and Rudesheim (plus the Kloster) would eat up two days. Perhaps adding a Rhine River tour for one day (plan getting on the boat from Biebrich and returning via train to Wiesbaden at the conclusion of the day). And with the car, you could take the one-hour drive up to the old Roman fort and Hessen-Park for one whole day of sight-seeing. Frankfurt? With a all-day ticket....may one day of sight-seeing. And if you had a fancy for German cars, tanks, and technology....there's the museum down in Speyer (one-hour away) which could consume one whole day (don't forget the Cathedral and city-walk). Oh, and Heidelberg is only an hour away by train.....if you wanted an old-city experience.
Cheap? No. Reasonable? Considering all the things you could see over a ten-day trip....maybe.