I followed the very same path, WR-841N v13 was not working. However, things are better now and
last images (building from master branch) look as being almost there, So you could give them a try.
WR-940N v6 has been working perfectly since some three months for two of our members, but firmware is custom-build and got many things removed, see my diff file:
CONFIG_TARGET_ar71xx=y
CONFIG_TARGET_ar71xx_tiny=y
CONFIG_TARGET_ar71xx_tiny_DEVICE_tl-wr940n-v6=y
CONFIG_BUSYBOX_CUSTOM=y
CONFIG_BUSYBOX_CONFIG_ADDGROUP=y
CONFIG_BUSYBOX_CONFIG_ADDUSER=y
CONFIG_BUSYBOX_CONFIG_FEATURE_ADDGROUP_LONG_OPTIONS=y
CONFIG_BUSYBOX_CONFIG_FEATURE_ADDUSER_LONG_OPTIONS=y
CONFIG_BUSYBOX_CONFIG_FEATURE_ADDUSER_TO_GROUP=y
CONFIG_BUSYBOX_CONFIG_FEATURE_CHECK_NAMES=y
# CONFIG_BUSYBOX_CONFIG_FEATURE_IPV6 is not set
CONFIG_BUSYBOX_CONFIG_FIRST_SYSTEM_ID=0
CONFIG_BUSYBOX_CONFIG_LAST_ID=0
CONFIG_BUSYBOX_CONFIG_LAST_SYSTEM_ID=0
CONFIG_BUSYBOX_DEFAULT_PIE=y
CONFIG_CLEAN_IPKG=y
# CONFIG_FEED_luci is not set
#CONFIG_FEED_telephony is not set
CONFIG_IMAGEOPT=y
# CONFIG_IPV6 is not set
# CONFIG_KERNEL_CRASHLOG is not set
# CONFIG_KERNEL_DEBUG_FS is not set
# CONFIG_KERNEL_DEBUG_INFO is not set
# CONFIG_KERNEL_DEBUG_KERNEL is not set
# CONFIG_KERNEL_ELF_CORE is not set
# CONFIG_KERNEL_IPV6 is not set
# CONFIG_KERNEL_MAGIC_SYSRQ is not set
# CONFIG_KERNEL_SWAP is not set
# CONFIG_PACKAGE_MAC80211_DEBUGFS is not set
# CONFIG_PACKAGE_MAC80211_MESH is not set
CONFIG_PACKAGE_iptables-mod-conntrack-extra=y
CONFIG_PACKAGE_iptables-mod-ipopt=y
CONFIG_PACKAGE_kmod-ifb=y
CONFIG_PACKAGE_kmod-ipt-conntrack-extra=y
CONFIG_PACKAGE_kmod-ipt-ipopt=y
# CONFIG_PACKAGE_kmod-nf-ipt6 is not set
CONFIG_PACKAGE_kmod-nls-base=y
CONFIG_PACKAGE_kmod-nls-utf8=y
# CONFIG_PACKAGE_kmod-ppp is not set
CONFIG_PACKAGE_kmod-sched-cake=y
CONFIG_PACKAGE_kmod-sched-core=y
# CONFIG_PACKAGE_libip6tc is not set
CONFIG_PACKAGE_libnetsnmp=y
# CONFIG_PACKAGE_odhcpd-ipv6only is not set
# CONFIG_PACKAGE_openwrt-keyring is not set
# CONFIG_PACKAGE_opkg is not set
# CONFIG_PACKAGE_ppp is not set
CONFIG_PACKAGE_snmpd=y
CONFIG_PACKAGE_sqm-scripts=y
CONFIG_PACKAGE_sqm-scripts-extra=y
CONFIG_PACKAGE_sudo=y
CONFIG_PACKAGE_tc=y
# CONFIG_PACKAGE_uboot-envtools is not set
# CONFIG_PACKAGE_uclient-fetch is not set
# CONFIG_PACKAGE_usign is not set
CONFIG_PKG_ASLR_PIE=y
# CONFIG_POSTFIX_CDB is not set
# CONFIG_POSTFIX_LDAP is not set
# CONFIG_POSTFIX_PCRE is not set
# CONFIG_POSTFIX_SASL is not set
# CONFIG_POSTFIX_SQLITE is not set
# CONFIG_POSTFIX_TLS is not set
# CONFIG_SIGNED_PACKAGES is not set
CONFIG_STRIP_KERNEL_EXPORTS=y
CONFIG_USE_MKLIBS=y
# CONFIG_BUSYBOX_CONFIG_PIE is not set
CONFIG_PACKAGE_kmod-lib-crc-ccitt=y
CONFIG_PACKAGE_libpthread=y
CONFIG_PACKAGE_libuclient=y
Hope this helps