I has been a decade from last time I used the engines default shaders and I needed to test it. I had no error report when set the new technique. Anyway, there is nothing called 'postView' into 'specBump.fx'. I guess it has to come from anywhere else.

Moreover, it seems 'DoSpecular' does not compute the specular reflection. It looks flat for me. I don't know what happens.

Also, there is another state I missed to include into the pass states inside the technique description:

AlphaTestEnable = True;

This state makes the shader avoid witting into depth stencil map on transparent pixels.

Here goes a full diffuse+specular shader out of the 3dgs default shaders

float3x3 matTangent;

float4x4 matWorldViewProj;
float4x4 matWorld;
float4 vecViewDir;
float4 vecLight;

int iLights;
float4 vecLightPos[8];
float4 vecLightColor[8];

texture entSkin1;
sampler TexSampler = sampler_state { Texture = <entSkin1>; Mipfilter = Linear; Minfilter = Linear; Magfilter = Linear; };
texture entSkin2;
sampler TNSampler = sampler_state { Texture = <entSkin2>; Mipfilter = Linear; Minfilter = Linear; Magfilter = Linear; };

void VS (
	in float4 inPos: POSITION,
	in float3 inNormal: NORMAL,
	in float2 inTex: TEXCOORD0,
	in float3 inTangent: TEXCOORD2,
	out float4 outPos: POSITION,
	out float3 outNormal: TEXCOORD0,
	out float3 outWorld: TEXCOORD1,
	out float2 outTex: TEXCOORD2,
	out float3 outTangent: TEXCOORD3) {
		outPos = mul(inPos, matWorldViewProj);
		outNormal = mul(inNormal, (float3x3)matWorld);
		outWorld = mul(inPos, matWorld).xyz;
		outTex.xy = inTex.xy;
		outTangent = mul( inTangent.xyz, (float3x3)matWorld );
float4 PS (
	in float3 inNormal: TEXCOORD0,
	in float3 inWorld: TEXCOORD1,
	in float2 inTex: TEXCOORD2,
	in float3 inTangent: TEXCOORD3) : COLOR0 {
		float4 Color = tex2D(TexSampler, inTex);
		float4 TNormalTex = tex2D(TNSampler, inTex);
		float3 bumpNormal = (TNormalTex.xyz * 2.0f) - 1.0f;
		inTangent = normalize(inTangent);
		inNormal = normalize(inNormal);
		float3 binormal = cross(inNormal, inTangent);
		float3 worldNormal = bumpNormal.x * inTangent + bumpNormal.y * binormal + bumpNormal.z * inNormal;
		float3 fDiffuse = vecLight.rgb;
		float3 fSpecular = 0;
		for(float i=0; i<iLights; i+=1) {
			float3 fDir = inWorld.xyz - vecLightPos[i].xyz;
			float3 fReflect = normalize((2.0f * dot(worldNormal, fDir) * worldNormal) - fDir);
			float fRadiance = saturate((vecLightPos[i].w - length(fDir)) / vecLightPos[i].w);
		   fSpecular += vecLightColor[i].rgb * pow(saturate(dot(fReflect, vecViewDir.xyz)), 8.0f) * TNormalTex.a;
			fDiffuse += vecLightColor[i].rgb * saturate(dot(normalize(-fDir), worldNormal.xyz)) * fRadiance;
		float4 FinalColor;
		FinalColor.rgb = Color.rgb * fDiffuse;
		FinalColor.rgb += fSpecular;
		FinalColor.a = Color.a;
		return FinalColor;

technique SpecTrans
	pass p0
		ZWriteEnable = True;
		AlphaBlendEnable = True;
		AlphaTestEnable = True;
		VertexShader = compile vs_3_0 VS();
		PixelShader  = compile ps_3_0 PS();

It computes the lights effect pixel side instead of vertex side as the defult 3dgs shader does. It looks much better but it is also much slower.