Plots.jl - Controlling dash pattern with PGFPlotsx Backend

I encountered following problem. The default settings of pgfplots produce dashed lines which are indistinguishable from dotted lines at larger line widths. Consider the MWE

using Plots
plot(x -> sin(x), line = (3, :dash))
plot!(x -> cos(x), line = (3, :dot))

Due to the line width of 3 the dashes are practically equal to the dots (problem vanishes at line = 1). This shouldn’t be a problem, since within LaTeX the dashed lines can be controlled with the dash pattern option and we can pass extra keyword arguments to LaTeX / PGFPlots. However, the needed .tex code should look like

dashed, dash pattern = on 8pt off 2pt

but using

plot(x -> sin(x), line = (3, dash), dash_pattern = "on 8pt off 2pt")

results in tex code of the form

dash pattern ={on 8pt off 2pt}, dashed

Right now I don’t know whether the additional curly brackets are the problem or the order of the options; however is there a way to control these?