General ⇒ Slashbox.sty mess up - any suggestions for alternatives?

[Medova]

When using the \backslashbox in a table, the line inserted totally mess up - it looks very bad, since the line is not straight and is conflicting with the text. (See the attached pdf)

The code for this table (have removed alle unnessesary code):

\begin{table}[!ht]
\centering
\begin{tabular}{l| c| c| c}
\multicolumn{1}{c|}{\backslashbox{\textbf{Consumption [kWh]}}{\textbf{OEE [\%]}}} & \textbf{Actual} & \textbf{Assumed} & \textbf{World class} \\
{Rest of the table is written here}

Any suggestions how to make this look good?