landlord tenant laws in WA state, after 3 years with no lease can landlord require a lease

You should review your facts and options with a local attorney.

Just going by the facts in the post and general WA law, there seems to be no legal issue against the landlord.

If you had not have an increase in rent in the last THREE years and is now getting a 10% increase, you likely are getting a good deal. If you check the property tax records in your county, you likely will find that the taxes against your landlord's property have increased. The insurance for the property likely had increased. Almost everything has increased in price in the last 3 years.

You can check the WA Residential landlord-tenant act (Chapter 59.18 RCW) to see whether the statutes would support a claim of retaliation. The statutes can be accessed here: http://apps.leg.wa.gov/RCW/default.aspx?cite=59.18 . The retaliation provisions are RCW 59.18.240 and RCW 59.18.250 .

You always have the option to move. Depending on how much rent you are paying now (including the increase) compared to the market, you may be able to find a better place to rent. You appear to be paying $450 now. In the Seattle area, likely there is no rental for that amount of rent.