E will bring down T on its own due to negative feedback at the hypothalamus and pituitary gland. As long as there is a decent concentration of sex hormones in the body, regardless of what they may be (P, E or T), the brain stops signalling the testes (or ovaries) to produce sex hormones because it senses there's enough.
Bio-identical estrogen taken non-orally has indeed been shown to be much safer, even in men of a certain age with advanced prostate cancer as the above link attests to. And shown to be effective on its own at reducing T to castrate levels.